CN117050155B - Polymerization site of amoeba perforin, screening method and application thereof - Google Patents
Polymerization site of amoeba perforin, screening method and application thereof Download PDFInfo
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- KHGNFPUMBJSZSM-UHFFFAOYSA-N Perforine Natural products COC1=C2CCC(O)C(CCC(C)(C)O)(OC)C2=NC2=C1C=CO2 KHGNFPUMBJSZSM-UHFFFAOYSA-N 0.000 title claims abstract description 21
- 229930192851 perforin Natural products 0.000 title claims abstract description 21
- 238000006116 polymerization reaction Methods 0.000 title abstract description 61
- 238000000034 method Methods 0.000 title abstract description 14
- 238000012216 screening Methods 0.000 title abstract description 8
- 241000224489 Amoeba Species 0.000 title description 13
- 239000000178 monomer Substances 0.000 claims abstract description 34
- 125000000539 amino acid group Chemical group 0.000 claims description 6
- 206010001986 Amoebic dysentery Diseases 0.000 abstract description 10
- 239000003814 drug Substances 0.000 abstract description 8
- 208000008710 Amebic Dysentery Diseases 0.000 abstract description 7
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- GOJUJUVQIVIZAV-UHFFFAOYSA-N 2-amino-4,6-dichloropyrimidine-5-carbaldehyde Chemical group NC1=NC(Cl)=C(C=O)C(Cl)=N1 GOJUJUVQIVIZAV-UHFFFAOYSA-N 0.000 description 1
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- MBYXEBXZARTUSS-QLWBXOBMSA-N Emetamine Natural products O(C)c1c(OC)cc2c(c(C[C@@H]3[C@H](CC)CN4[C@H](c5c(cc(OC)c(OC)c5)CC4)C3)ncc2)c1 MBYXEBXZARTUSS-QLWBXOBMSA-N 0.000 description 1
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- VAOCPAMSLUNLGC-UHFFFAOYSA-N metronidazole Chemical compound CC1=NC=C([N+]([O-])=O)N1CCO VAOCPAMSLUNLGC-UHFFFAOYSA-N 0.000 description 1
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- JLYXXMFPNIAWKQ-UHFFFAOYSA-N γ Benzene hexachloride Chemical compound ClC1C(Cl)C(Cl)C(Cl)C(Cl)C1Cl JLYXXMFPNIAWKQ-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07K—PEPTIDES
- C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
- C07K14/435—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
- C07K14/44—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans from protozoa
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K45/00—Medicinal preparations containing active ingredients not provided for in groups A61K31/00 - A61K41/00
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
- A61P33/00—Antiparasitic agents
- A61P33/02—Antiprotozoals, e.g. for leishmaniasis, trichomoniasis, toxoplasmosis
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
- G01N33/68—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving proteins, peptides or amino acids
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
- G01N33/68—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving proteins, peptides or amino acids
- G01N33/6893—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving proteins, peptides or amino acids related to diseases not provided for elsewhere
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2333/00—Assays involving biological materials from specific organisms or of a specific nature
- G01N2333/435—Assays involving biological materials from specific organisms or of a specific nature from animals; from humans
- G01N2333/44—Assays involving biological materials from specific organisms or of a specific nature from animals; from humans from protozoa
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2800/00—Detection or diagnosis of diseases
- G01N2800/26—Infectious diseases, e.g. generalised sepsis
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/30—Against vector-borne diseases, e.g. mosquito-borne, fly-borne, tick-borne or waterborne diseases whose impact is exacerbated by climate change
Abstract
The invention relates to a polymerization site of amoxypyr, a screening method and application thereof, and relates to the technical field of medical engineering. The polymerization site is a Glu2 charged residue side chain of an amebock perforin monomer and/or a Lys37 charged residue side chain of the amebock perforin monomer. The polymerization site provides a new action target for developing a drug capable of resisting amebic dysentery.
Description
Technical Field
The invention relates to the technical field of medical engineering, in particular to a polymerization site of amoxypyr, a screening method and application thereof.
Background
The combined infection of amebic dysentery and AIDS is in an ascending trend and can become complications of liver cirrhosis and diabetes. The amoeba disease is caused by amoeba in the dissolved tissues, can be transmitted among people through polluted water, food, mosquitoes, chronic infectious people and the like, causes hyperpyrexia, dysentery, colonitis and intestinal perforation of patients, can cause metastatic extra-intestinal infection of organs such as liver, lung, brain and the like, causes serious tissue abscess and damage, and seriously endangers the health of people. The existing common medicines for resisting amebic dysentery comprise metronidazole, emetine, quinoline and the like, but have strong side effects, high recurrence rate and serious drug resistance problem; patients with pop-type, bowel perforation, and metastatic abscess have poor prognosis.
Amoeba Perforin (APA) is a key pathogenic protein secreted by amoeba histolytica, and can secrete APA after the amoeba adheres to target cells, APA self-polymerizes on the target cell membrane to affect the permeability of the target cells, leading to cell lysis, death and phagocytosis. Thus, the polymerization site of APA may be a potential target against amebic dysentery. However, no studies have yet confirmed the polymerization sites of APA and their active mechanism at the molecular level.
Disclosure of Invention
Aiming at the problems, the invention provides a polymerization site of amoxynil, which provides a new action target for developing a drug capable of resisting amoxynil dysentery.
In order to achieve the above object, the present invention provides a polymerization site of amoperforin, wherein the polymerization site is a Glu2 charged residue side chain of amoperforin monomer and/or a Lys37 charged residue side chain of amoperforin monomer.
In previous studies, it was found that the killing activity of APA against target cells was dependent on pH-mediated self-polymerization mechanisms. In a weak acid environment with ph=5.2, APA can self-polymerize on the target cell surface to form dimer to hexamer polymers, where the transmembrane activity reaches the highest, resulting in destruction of the target cell membrane. And, down-regulating or silencing APA gene can obviously reduce the killing property of amoeba histolytica to eukaryotic cells. Thus, self-polymerization of APA is a necessary condition for its activity, which must be achieved through efficient polymerization sites. The inventor evaluates the molecular weight of APA under different physical conditions (such as pH and protein concentration) by using 1D NMR technology, judges the polymerization rule, tracks the signal displacement of APA residue under different physical conditions by using isotope labeling and 2D and 3D NMR, and calculates the residue side chain pKa capable of exciting dimer formation. Combining the result and the molecular structure, analyzing the polymerization site of APA and establishing a model of the polymerization structure. The model is verified by using a small-angle X-ray scattering technology, so that the polymerization site of the APA dimer is confirmed, and the role of the polymerization site in an APA activity mechanism is clarified. The polymerization site can provide a new action target for the amoebic dysentery resisting medicine.
In one embodiment, the Glu2 charged residue side chain is amino acid residue No. 2 of the amebock perforin monomer and the Lys37 charged residue side chain is amino acid residue No. 37 of the amebock perforin monomer.
In one embodiment, the Glu2 charged residue side chain is located at the front of the 1 st alpha helix of the two-dimensional structure of the amebic perforin monomer; the Lys37 charged residue side chain is positioned between the 3 rd alpha helix and the 4 th alpha helix of the two-dimensional structure of the amoxycillin monomer.
The invention also provides a screening method of the polymerization sites, which comprises the following steps: the amebic perforin monomer is placed in a buffer solution, the pH value is adjusted, and one-dimensional liquid nuclear magnetic resonance is adopted to detect the molecular weight, so that the pH value of the monomer taking amebic perforin as the monomer and the pH value of the dimer taking amebic perforin as the dimer are obtained; setting the pH value as a monomer pH value or a dimer pH value, adjusting the concentration of amoeba perforin monomers, detecting signal displacement by adopting heteronuclear single quantum coherent nuclear magnetic resonance, measuring the signal displacement distance, calculating the absolute difference value of the signal displacement distance, setting a threshold value, comparing the signal displacement distance with the threshold value, and screening to obtain a polymerization site.
In one embodiment, the method for calculating the threshold value includes: the standard deviation of the signal displacement distance is subtracted from the absolute difference of the signal displacement distance to obtain an average value.
In one embodiment, the screening method further comprises verification, the verification comprising: measuring the pKa value of the polymerization site using 2D and/or 3D NMR, compared to the natural pKa value of the charged residue side chain;
or the verification includes: the pH value is set to be the monomer pH value or the dimer pH value, the concentration of the amoperforin monomer is adjusted, the SAXS is adopted to calculate the size of the amoperforin monomer or the amoperforin dimer, modeling is carried out, and the polymerization site is analyzed.
The invention also provides an amoperforin dimer, which comprises 2 amoperforin monomers, wherein the Glu2 charged residue side chain of one amoperforin monomer is combined with the Lys37 charged residue side chain of the other amoperforin monomer through electrostatic action to form a salt bridge.
In one embodiment, the Glu2 charged residue side chain is located at the front of the 1 st alpha helix of the two-dimensional structure of amebocyte, and the Lys37 charged residue side chain is located between the 3 rd alpha helix and the 4 th alpha helix of the two-dimensional structure of amebocyte.
In one embodiment, the pKa value of the side chain of the Glu2 charged residue is 3.90+ -0.06, the structure of the amoperforin dimer has a radius of 11-12A and a longest diameter of 45-49A.
The invention also provides an amebock perforin mutant, wherein the amino acid residue No. 2 of an amebock perforin monomer is Gln, and the amino acid residue No. 37 is Gln.
The inventors constructed APA mutants based on the polymerization sites of the established dimer models, which mutated Glu2 charged residue side chain and Lys37 charged residue side chain of the polymerization sites into glutamine (Gln), which is an uncharged polar amino acid, by a point mutation method, aiming at breaking salt bridges originally formed by electrostatic bonding, so that APA monomers cannot polymerize to form dimers. The result shows that the polymerization capacity and the membrane penetration activity of APA are obviously reduced or eliminated after mutation of the key polymerization site, which indicates that the discovered APA polymerization site (Glu 2 charged residue side chain and Lys37 charged residue side chain) plays a key role in the polymerization and membrane penetration activity of the APA, and the amoeba perforin mutant can provide ideas for drug development, treatment and prevention of amoebic dysentery.
The invention also provides application of the polymerization site serving as a target spot in preparation of therapeutic drugs, detection reagents or diagnostic kits;
or the application of the inhibitor of the polymerization site in preparing therapeutic drugs, detection reagents or diagnostic kits.
In one embodiment, the therapeutic agent comprises an agent for treating amebic dysentery; the detection reagent comprises a reagent for detecting amoeba; the diagnostic kit comprises a kit for diagnosing amebic dysentery.
The invention also provides the application of the structure or the amoxycillin mutant in preparing therapeutic drugs, detection reagents or diagnostic kits.
Compared with the prior art, the invention has the following beneficial effects:
according to the polymerization site of the amoxyporin, the screening method and the application thereof, disclosed by the invention, the polymerization site of the amoxyporin can influence the dimerization mechanism of the amoxyporin, so that mutation or inactivation of the polymerization site can cause the amoxyporin to lose the membrane penetrating activity, and a new action target point is provided for developing a drug capable of resisting amoxyporin.
Drawings
FIG. 1 is a graph showing the results of 1D NMR estimation of APA molecular weight at different pH values in example 1;
FIG. 2 is a graph showing the results of construction of an APA dimer model by NMR in example 1, wherein A is a 2D HSQC NMR spectrum and B is an APA dimer structure constructed by Pymol and HADDOCK;
FIG. 3 is a graph of SAXS scattering data at various APA concentrations and pH values for example 1;
FIG. 4 is a 2D HSQC NMR spectrum of APA mutant E2Q-K37Q in example 1;
FIG. 5 is a graph showing the results of the APA mutant self-polymerization experiment in example 1, and the polymerization behavior of APA mutant E2Q-K37Q and wild-type (wt) APA was verified by analytical size exclusion chromatography at pH=5.2, 50. Mu.M;
FIG. 6 is a graph showing real-time results of QCM-D binding of APA to cell membrane in example 1, wherein A is a graph showing interaction results of APA mutant E2Q-K37Q with cell membrane; b is a graph showing the interaction result of wild-type APA with cell membrane.
Detailed Description
In order that the invention may be readily understood, a more complete description of the invention will be rendered by reference to the appended drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Definition:
the amoeba of the invention: refers to parasites that cause amebic dysentery.
APA: amebic perforin, an ion channel-like protein secreted by amebic protozoa.
1D NMR: refers to one-dimensional liquid nuclear magnetic resonance.
2D NMR: refers to two-dimensional liquid nuclear magnetic resonance.
3D NMR: refers to three-dimensional liquid nuclear magnetic resonance.
HSQC NMR: refers to heteronuclear single quantum coherent nuclear magnetic resonance.
SAXS: refers to small angle X-ray scattering.
IMAC: refers to a metal chelate affinity chromatography stationary phase.
RP-HPLC: refers to reversed phase high performance liquid chromatography.
QCM-D: refers to a quartz crystal microbalance.
The reagents, materials and equipment used in the examples are all commercially available sources unless otherwise specified; the experimental methods are all routine experimental methods in the field unless specified.
Example 1
1. Synthesis and purification of APA.
APA cannot be expressed using conventional cell systems because of its antibacterial properties, and extraction of APA from Enamoeba histolytica is inefficient. Thus, the present inventors successfully expressed and purified APA using cell-free protein synthesis technology, and examined that the transmembrane activity was 25pmol. The above cell-free protein synthesis techniques have been disclosed in the following documents: cell-free synthesis and combinatorial selective N-labeling of the cytotoxic protein amoebapore A from Entamoeba histolytica; pages 22-7 of volume 1, 2009, volume 68, protein expression and purification.
2. The effect of pH on APA polymerization was examined.
1D NMR is a rapid technique for assessing folding of three-dimensional structures of proteins and estimating the size of proteins. In the 1D NMR spectrum, the amide and methylated proton signals are the basis for assessing the APA structure, and the transverse relaxation time T2 can be used to estimate the approximate size of the APA, with the formula tc=1/(5× (T2/1000)), tc being the estimated molecular size.
The inventors estimated the molecular weight of 50. Mu.M APA at pH3, 5.5, 8.5, 5.2 (reversible measurement), 3 (reversible measurement) using 1D NMR experiments, all run on a Bruker AV600 Nuclear magnetic resonance apparatus at 25℃with specific manipulations of placing APA at a concentration of 50. Mu.M in 20mM sodium phosphate buffer followed by pH adjustment using 1M HCL or NaOH.
The results show that APA molecular weight increases with increasing pH, polymerizing between pH 5.2-8.5; when the pH was reduced from 8 to 3.0, the APA recovered to monomer, indicating that the APA polymerized as pH dependent and as a reversible mechanism, the results are shown in fig. 1.
3. An APA dimer model was constructed using NMR.
2D HSQC NMR is a technique for accurately detecting changes in protein structure under different physical conditions (pH and protein concentration). When APA forms dimers from monomers, the residual genes at the dimer interface undergo a change in the surrounding charge environment resulting in a shift in their corresponding signals on the NMR spectrum, and 2D HSQC NMR can be used to search for the polymerization sites to which APA dimers bind.
The inventors measured and compared signal shifts in NMR spectra for different concentrations of APA at pH3 and 5.2. Two sets of experiments were performed:
1. comparing the NMR spectra generated at different pH (3 and 5.2) at the same APA concentration;
2. NMR spectra generated by comparing APA at different concentrations (10. Mu.M and 2.5 mM) at the same pH;
measuring the signal displacement distance in the map, and calculating the absolute difference value of the signal displacement distance according to the following formula:
wherein,is the shift of monomer and/or dimer APA residues on the NMR spectrum in ppm; />Is the displacement of APA monomer on the NMR spectrum, with the unit being ppm; />Is the shift of the APA dimer on the NMR spectrum in ppm;is the dissociation constant of APA; [ APA ]]Protein concentration for APA.
Taking the average of the absolute differences of the signal displacement distances above the standard deviation as a threshold (i.e., the standard deviation of the signal displacement distances minus the absolute difference of the signal displacement distances, then taking the average), any APA residues corresponding to signal displacements that differ significantly from the threshold are considered to have a strong pH or APA concentration dependence.
The results show that when the APA concentration is increased or the pH is increased, the NMR signal corresponding to a portion of the residues is significantly shifted and broadened, indicating that it is likely to be located at the dimer polymerization surface. After normalized calculation of all NMR residue signal shifts, an APA dimer interface is estimated according to the signal shift result, and an APA dimer structure is constructed by using Pymol and docking software HADDOCK (as shown in figure 2), wherein A is a 2D HSQC NMR spectrum in figure 2, and B is an APA dimer structure constructed by using Pymol and HADDOCK; wherein the charged Glu2 and Lys37 residues undergo the most significant signal shift and play a key role in APA polymerization. In this structure, glu2 and Lys37 residues located on the polymerization side of the dimer are likely to mediate dimer formation, a critical polymerization site.
The side chain of the Glu2 charged residue is the No. 2 amino acid residue of the amebock perforin monomer, and is positioned at the front end of the 1 st alpha helix of the two-dimensional structure of the amebock perforin monomer, and the side chain of the Lys37 charged residue is positioned between the 3 rd alpha helix and the 4 th alpha helix of the two-dimensional structure of the amebock perforin monomer.
4. The pKa of the side chain of the residue was measured to aid modeling.
2D/3D NMR was used to measure the pKa value of the side chains of charged residues of APA to further determine the polymerization sites for APA dimer formation.
When APA polymerizes, the chemical environment around the electrical residues of the corresponding domains of the polymerization surface changes drastically, resulting in a pKa of the charged residues that is different from the normal value. The inventors performed this experiment using eight NMR experimental procedures (3D HCCH TOCSY, 2D CBCAHN, 2D CTHSQC1, 3D HBHANH, 3D 15N-rim TOCSY, 2D HCCO, 3DHCCO, 2D CTHSQC2). The pH range was 2-8.5, the unit pH was 0.5, and all experiments were performed at 25 ℃. After the program is finished, the displacement of the signal point of the side chain of the residue along with the change of pH is recorded by NMRAnalysis software, and curve fitting is performed by using a Henderson Hasselbalch Hill equation, wherein the formula is as follows:
in ppm, is the displacement of the side chain of the residue observed in the NMR spectrum; />Is the displacement limit reached by the side chain of the residue in the acid state, and the unit is ppm; />The side chains of residues being accessible in the alkaline stateDisplacement limit in ppm; pKa is the dissociation constant, the same as pH units; n is the Hill coefficient.
Finally, the pKa was calculated using Python software. Comparing the estimated pKa value of the residue side chain with the natural value, the actual pKa value (3.90+/-0.06) of the Glu2 residue side chain positioned on the polymerization surface of the APA dimer model is found to be obviously lower than the normal value (pKa=4.2), further the critical site of Glu2 possibly for APA polymerization is determined, and the structure of the APA dimer is verified. Since the Kd of Lys37 residue is too large to be measured by NMR, the dimer model will be further validated using SAXS.
5. The APA dimer model was validated using SAXS.
SAXS is a low resolution technique for estimating protein size and structure under different physical conditions.
The inventors performed SAXS experiments at ph3.0 and 5.2 and at different APA concentrations (0.55 mM-2.1 mM), all experiments were performed at 25 ℃. Analyzing the processed SAXS scattering data by using methods of Rg, dmax, P (r), GNOM, CRYSOL and the like, and estimating the APA structure size; the APA structure was modeled using software such as GASBOR, DAMMAVER, DAMFILT and supbeomb.
The results show that the higher the APA concentration, the more significant the difference in molecular size at ph=3 and 5.2 (as shown in fig. 3). The inventors analyzed SAXS scattering data and calculated that at ph=5.2, the dimer radius of high concentration APA was about 11 a and the longest diameter was about 45 a, consistent with the model of the APA dimer structure constructed by the inventors (radius=12 a and longest diameter=49 a). Depending on the length and width of the APA dimer structure (APA is not a perfect circle structure), and the location of the salt bridge and the energy-based protein docking results, there are two general structural models conforming to the APA dimer, one is a dimer model with a length of 43A, a height of 33A (radius of about 17) and a height of 23A (radius of about 12) formed by combining H75 with D63 and K64 with E2, and the other is a dimer model with a length of 49A, a height of 23A (radius of about 12) formed by combining E2 (i.e., glu 2) with K37 (i.e., lys 37) proposed by the present invention. After the SAXS experiment is completed, the data are modeled by using DAMAVER and DAMFILT software to obtain 10 optimal GASBOR models, and a dimer model with the length of 49A and the radius of 12A is obtained by averaging 10 models, wherein the model accords with an APA dimer model formed after a salt bridge is formed by E2-K37 and provided by the group. By adding the E2 and K37 shift results of NMR, E2 (i.e., glu 2) and K37 (i.e., lys 37) were confirmed as polymerization sites, and the above APA dimer structure and polymerization sites thereof were further confirmed, and Lys37 was within the polymerization site range.
In the polymerization process of the amoxycillin monomer, a Glu2 charged residue side chain at the front end of the 1 st alpha helix of the two-dimensional structure of the amoxycillin monomer is combined with a Lys37 charged residue side chain between the 3 rd alpha helix and the 4 th alpha helix of the two-dimensional structure of the amoxycillin monomer through electrostatic action to form a salt bridge, so as to form the amoxycillin dimer.
6. APA mutants were designed and constructed.
The inventor designs, expresses and purifies an APA double-residue mutant E2Q-K37Q according to the structure of the APA dimer, and aims to destroy the structure of the APA dimer, thereby further verifying the influence of two polymerization sites of Glu2 and Lys37, which mediate dimer occurrence, on the APA membrane penetration activity.
The construction method of the APA double-residue mutant E2Q-K37Q specifically comprises the following steps: the mutation of Glu2 with negatively charged side chain in APA monomer is replaced by uncharged Gln2, and the mutation of Lys37 with positively charged side chain is replaced by uncharged Gln by utilizing the conventional site-directed mutagenesis technology, so that the Glu2 (E2) -Lys37 (K37) salt bridge of the bonding surface of the APA dimer is broken, and the bonding surface condition of the dimer is confirmed by utilizing the bonding condition of the mutant and lipid.
After obtaining the APA mutants, the inventors first evaluated their three-dimensional structure using 1D and 2D NMR. The results show that the three-dimensional structure of the APA mutant is similar to that of the natural APA, and the APA double-residue mutant E2Q-K37Q obtained by the construction method has the structure which is not obviously different from that of a conventional APA monomer, has a good three-dimensional structure which is well preserved and is suitable for the next experiment (shown in figure 4), and two signals in each NMR spectrum in figure 4 can be approximately overlapped, so that the three-dimensional structure of the point mutation APA is generally normal and is suitable for the subsequent experiment.
7. Self-polymerization of APA mutants was verified.
To further define the polymerization sites of APA dimers, the inventors tested the polymerization ability of wild-type and APA mutants E2Q-K37Q using analytical size exclusion chromatography at ph=5.2, protein concentration=50 μm.
The results show that the APA mutant E2Q-K37Q was unable to normally form dimers compared to wild-type APA (as shown in fig. 5), further confirming the above dimer model of APA and two key polymerization sites of Glu2 charged residue side chain and Lys37 charged residue side chain.
8. The penetrating activity of the APA mutant was verified by QCM.
Quartz crystal microbalance technology (QCM-D) is a highly sensitive instrument for real-time and rapid monitoring of protein interactions with cell membranes. The cell membrane is formed on the quartz crystal between the electrodes, and when a voltage is applied to the crystal, the instrument reflects the real-time dynamics of APA-cell membrane binding by monitoring the vibration frequency and energy dissipation of the crystal reference overtones.
The inventors prepared a bilayer lipid cell membrane using a cell membrane lipid mixed solution, and fully optimized experimental conditions for cell membrane formation for testing interactions of wild-type APA and APA mutant E2Q-K37Q with cell membranes, all experiments were performed at room temperature at ph=5.2.
The results show that wild-type APA can transiently cross vertically into the interior of a cell membrane and subsequently carry away large amounts of lipids from the cell membrane, resulting in disruption of the cell membrane. In contrast, the APA mutant E2Q-K37Q stays on the surface of the cell membrane, even if the APA mutant is added to the cell membrane for many times, the APA mutant E2Q-K37Q has no obvious influence on the structure and the stability of the cell membrane (as shown in FIG. 6), in FIG. 6, the interaction between the APA mutant E2Q-K37Q and the cell membrane is shown, the cell membrane structure is not obviously changed along with the multiple addition of the APA, and the APA mutant E2Q-K37Q is Frequency Energy dissipation of the from left to right in sequence in the boxes th overtone、Frequency Energy dissipation of the 7 th overtone、Frequency Energy dissipation of the 9 th overtone、Frequency Energy dissipation of the 11 th overtone、Frequency Energy dissipation of the 13 th An alert; b is the interaction of wild APA and cell membrane, the cell membrane has obvious structural change in each layer after APA is added, and a large amount of phospholipid is lost, and Frequency Energy dissipation of the 5 is arranged in sequence from left to right in the box th overtone、Frequency Energy dissipation of the 7 th overtone、Frequency Energy dissipation of the 9 th overtone、Frequency Energy dissipation of the 11 th overtone、Frequency Energy dissipation of the 13 th overtone。
Taken together, the above experiments demonstrate that APA has a broad killing potential and polymerizes under pH adjustment, while dimer formation is a prerequisite for APA production activity. The inventors have experimentally determined the polymerization phenomenon of APA, which is regulated not only by pH but also by the concentration of the protein itself. Meanwhile, the inventor constructs an APA dimer structure and defines the key polymerization sites of polymerization. APA is used as a key pathogenic protein secreted by Enamoeba histolytica, the occurrence of APA dimer is a key factor of the membrane penetration activity of APA, the side chain of Glu2 charged residue and the side chain of Lys37 charged residue are key polymerization sites for mediating the occurrence of dimer, once mutation occurs, the dimerization mechanism of APA is influenced, so that the APA further loses the membrane penetration activity, the APA dimer can be used as a potential target point of an amoeba resistant medicament, and the polymerization sites can be defined to provide key basis for potential medicament development and treatment and prevention of amoebic dysentery.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (1)
1. An amebock perforin mutant characterized in that amino acid residue No. 2 of amebock perforin monomer is gin and amino acid residue No. 37 is gin.
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| Title |
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| Primary and secondary structure of the pore-forming peptide of pathogenic Entamoeba histolytica;Leippe等;《THE EMBO JOURNAL》;第11卷(第10期);第3501-3506页 * |
| Solution Structure of the Pore-forming Protein of Entamoeba histolytica;Oliver Hecht等;《THE JOURNAL OF BIOLOGICAL CHEMISTRY》;第279卷(第17期);第17834-17841页 * |
| 溶组织内阿米巴:Gal/GalNAC凝集素轻亚单位上GPI锚信号序列的缺失阻止其组装成凝集素异二聚体;罗玉倩;国外医学.寄生虫病分册(第02期);第88-89页 * |
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