title: Molecular dynamics studies on the thermostability of family 11 xylanases.
abstract: Twelve members of the family 11 xylanases, including both mesophilic and thermophilic proteins, were studied using molecular dynamics (MD). Simulations of xylanases were carried out in an explicit water environment at four different temperatures, 300, 400, 500 and 600 K. A difference in thermotolerance between mesophilic and thermophilic xylanases became clear: thermophilic xylanases endured heat in higher simulation temperatures better than mesophilic ones. The unfolding pathways seemed to be similar for all simulations regardless of the protein. The unfolding initiates at the N-terminal region or alternatively from the alpha-helix region and proceeds to the 'finger region'. Unfolding of these regions led to denaturated structures within the 4.5 ns simulation at 600 K. The results are in agreement with experimental mutant studies. The results show clearly that the stability of the protein is not evenly distributed over the whole structure. The MD analysis suggests regions in the protein structure which are more unstable and thus potential targets for mutation experiments to improve thermostability.
authors.affiliation: Department of Chemistry, University of Joensuu, PO Box 111, 80101 Joensuu, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Purmonen
authors.forename: Jarkko
authors.initials: J
authors.lastname: Valjakka
authors.forename: Kristiina
authors.initials: K
authors.lastname: Takkinen
authors.forename: Tuomo
authors.initials: T
authors.lastname: Laitinen
authors.forename: Juha
authors.initials: J
authors.lastname: Rouvinen
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000145:classification / Q000378:metabolism; D003198:Computer Simulation; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry* / Q000145:classification* / Q000378:metabolism; D004795:Enzyme Stability; D005656:Fungal Proteins / Q000737:chemistry / Q000145:classification / Q000378:metabolism; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D005656:Fungal Proteins; D043364:Endo-1,4-beta Xylanases