title: Thermostability Mechanism for the Hyperthermophilicity of Extremophile Cellulase TmCel12A: Implied from Molecular Dynamics Simulation.
abstract: Thermostability is of considerable importance for the application of cellulase in cellulosic ethanol production. The cellulase 12A from the hyperthermophile Thermotoga maritima (TmCel12A) is an ideal candidate to study thermostability of cellulases. Optimal temperature of the wild-type enzyme is 85 °C. Recently, it has been observed that surface loop mutation Y61G not only accelerates the hydrolysis rate but also extends the half-life of the enzyme at high temperature. However, the mechanism of how Y61G enhances thermostability of TmCel12A has not been revealed. Here, molecular dynamics simulation together with dynamic correlation network analysis was used to explore thermostability mechanism of TmCel12A. A hydrophobic cluster constructed by Y61, W176, V62, and L144 in the binding pocket was found to play a pivotal role in modulating thermostability as well as catalytic capability of TmCel12A. It stabilizes the apoenzyme at high temperature; however, it impedes the substrate binding. Y61G mutation disturbs the hydrophobic cluster as the counterpart amino acid W176 forms a cation-π interaction with R60 instead of the π-π interaction with Y61 in WT. Moreover, Y61G mutation makes the enzyme more rigid and more extended via altering the amino acid communities at the hinge part of the enzyme. An earlier hypothesis proposed from crystallographic observation that Y61G may accelerate the products releasing has been also confirmed by our simulations. These findings may provide a new direction for both theoretical and experimental scientists to improve the thermostability of other cellulases that can be potentially applied in biofuel industry.
authors.affiliation: Department of Medicinal Chemistry & Key Laboratory of Smart Drug Delivery, Ministry of Education, School of Pharmacy, Fudan University , Shanghai 201203, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Lian
authors.affiliation: Department of Medicinal Chemistry & Key Laboratory of Smart Drug Delivery, Ministry of Education, School of Pharmacy, Fudan University , Shanghai 201203, China.
authors.forename: Congmin
authors.initials: C
authors.lastname: Yuan
authors.affiliation: State Key Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University , Shanghai 200240, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Department of Medicinal Chemistry & Key Laboratory of Smart Drug Delivery, Ministry of Education, School of Pharmacy, Fudan University , Shanghai 201203, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Fu
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D020134:Catalytic Domain; D002480:Cellulase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004795:Enzyme Stability; D056004:Molecular Dynamics Simulation; D016297:Mutagenesis, Site-Directed; D013379:Substrate Specificity; D013696:Temperature; D020124:Thermotoga maritima / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D002480:Cellulase