Theoretical Study On Cyclodextrin-Azobenzene Supramolecular Switch Regulating The Function Of Glutathione S-Transferase

With the continuous deepening of supramolecular chemistry research,the combination of natural enzymes and supramolecular switches has become more and more widely used in practical scenarios such as enzyme function regulation.Glutathione sulfur transferase(GST)is often found in mammals,plants,birds,insects,and microorganisms,and it plays an important role in detoxification,anti-oxidation,anti-tumor,and improving immunity.The resolved crystal structure is a symmetric homodimer,which provides favorable conditions for the modification of supramolecular switches.Cyclodextrin(CD)molecular switch gating is divided into three types: ?,?,and ?,which can envelop guest molecules of different sizes to form a host-guest complex that can regulate natural enzymes.Azobenzene molecule has a clear trans conformation in dark environment and visible light environment,but if it is exposed to ultraviolet light,its conformation will change from trans to cis,which makes it possible to pass cis and trans as guest molecules Isomerization to achieve the regulation of enzyme function.At the same time,the conformation change of azobenzene is a reversible process.With this reversible photoisomerization property,the cyclodextrin-azobenzene composite structure becomes an excellent combination for building smart enzymes that respond to light stimulation.Based on the above-mentioned host-guest interaction of cyclodextrin-azobenzene,this study uses molecular docking method to combine cyclodextrin and maleimide-modified azobenzene molecules to construct a supramolecular switch.The supramolecular switch is selectively modified in glutathione sulfur transferase(GST).Then,use different force field parameters to combine different size cyclodextrins and different modification sites and carry out molecular dynamics simulations.The specific research content and research results are as follows:Based on the analysis of the crystal structure of GST,select 117 and 124 to introduce Cys for substitution;At the same time,the azobenzene was modified with maleimide,and the synthesized azobenzene derivative Azo-MAM was used as the guest molecule to compound with the ?-CD/?-CD host molecule,and then the trans force field was applied for molecular dynamics.(Molecular dynamics,MD)simulation.This part of the research on the trans-force field includes the following six simulation systems: ?-CD combined with azobenzene derivative Azo-MAM modified at position 117(trans-?117),?-CD and azo modified at position 124 The combination of benzene derivative Azo-MAM(trans-?124),?-CD and Azo-MAM modified at positions 117 and 124(trans-?117/124)and ?-CD as the main molecule are different Three simulation systems of trans-?117,trans-?124 and trans-?117/124 with modified sites.(1)The simulation results show that in the three simulated systems that bind?-CD,the binding affinity of azobenzene molecules and ?-CD is stronger than that of the three simulated systems that bind ?-CD.The combination of ?-CD can construct a more stable host-guest complex system and increase the compactness of the protein structure.At this time,the cyclodextrin has a higher blocking efficiency and a better effect on the catalytic pockets.Through the analysis of the simulation trajectory,the reasons for the difference of cyclodextrins of different sizes in regulating GST activity are clarified.(2)Perform trajectory analysis on the three simulation systems trans-?117,trans-?124 and trans-?117/124 combined with ?-CD,explore the influence of different substitution sites on protein conformation changes,and draw the following conclusions: Azo The modification of the benzene derivative Azo-MAM at the Cys117 site is very important for the "on/off" allosteric of the hydrophobic cavity inside the GST.Specifically,the protein structure modified at Cys117 site is less active in the ?-helix region of the protein where the supramolecular switch is located,the domain is tighter and has lower hydrophobicity.These characteristics can stabilize the binding of cyclodextrin and GST.The crystal structure figure analyzed by GST shows that the catalytic center of GST is located inside the hydrophobic cavity,which is the middle position of the catalytic channel,and the position of Cys117 is closer to the catalytic pocket.This part of the work shows that the selection of modification sites is of great significance.(3)In order to explore the factors that affect the activity of supramolecular switches,the above six simulation systems were combined with the cis force field.Through molecular dynamics simulation,the maleimide-modified cis conformation(cis)azobenzene was combined with Cyclodextrin(?-CD and ?-CD)combined,and then constructed six new simulation systems cis-?117,cis-?124,cis-?117/124 and cis-?117,cis-?124,cis-?117/124.To simulate the conformational state of GST when the supramolecular switch is "on".The simulation results show that when the azobenzene molecule is in the cis conformation(the switch is turned on),?-CD is more difficult to dissociate from the azobenzene molecule because of its higher binding to GST;and ?-CD is the main body of the supramolecular switch When it is a molecule,the force formed between it and azobenzene and GST is smaller,making it more vigorous as a switch.The results of molecular dynamics simulations provide an important theoretical basis for exploring the control of the cyclodextrin-azobenzene supramolecular switch to control the catalytic efficiency of GST,and also for the design of supramolecular switches,improving the catalytic efficiency of enzymes,and improving the design of enzymes in the future.The program provides effective ideas.