Study On Homology Modeling And Molecular-docking Simulation Of Cellulase E4

The cellulose is one kind of renewable resources with the most widely distribution andthe richest content in nature. Replacing the petroleum with cellulose to produce bio-fuel andchemicals was already considered as an efficient way to solve the issue of energy crisis andenvironmental pollution. The key limitation was the transforming efficiency of cellulase whichtransforms cellulose to fermentable sugars. The artificial evolution and dock study on E4isdue to guideline the protein mutation, then promote the cellulase activity on the crystallinecellulose and reduce the cost in transforming cellulose to produce bio-fuel.To study the cellulase E4we first need to obtain the crystal structure of the enzyme,butso far, the enzyme do not have the complete crystal structure. We need to build the modelwith homology modeling method.Refers to the related literature,this study focus on twoamino acid mutations,hoping to increase the cellulase’s efficiency.Searching the databasewith target sequence,we build the homology model of E4,evaluate it and optimize itrepeatedly.Then, the optimized cellulase model is used to cellulose molecular binding docking.Explore the amino acid sites which plays an important role in the combination withsubstrate.It’s found that the enzyme amino acid residues ASN470、THR471、GLU478、LYS480、GLN522、ARG557、GLN561form a hydrogen bond network with substratecellulose.Refers to the literature, two amino acid residues PHE476, TYR520are locatedaround the binding pocket.Speculated that the improvement of activity on crystal structure isdue to the removal of the benzene ring around the pocket，resulting in the better combinationof the enzyme and cellulose. Based on this speculation, we choose the residues around thepocket which contain benzene ring to be mutated to alanine,then study its bind mechanismwith bioinformatics analysis and molecular biology experiments.We build two sets of homology model of E4which own the mutated residues,optimizethem and dock them to the substrate. From the results,we found that the models meet theenergy and spatial structure requirement,the docking result shows that the enzyme amino acidresidues ASN470、THR471、GLN522、ARG557、GLN561form hydrogen bond networks withsubstrate cellulose，the hydrogen network changes little.Because the binding enviroment ofenzyme and cellulose is very complex,the bioinformatics method could not simulate itcompletely.In this study,we made a preliminary study on the combination of cellulase E4andcellulose chain,if the two sets of mutations can promote the cellulase’s efficiency on crystalstructure we need further study.