title: The role of local residue environmental changes in thermostable mutants of the GH11 xylanase from Bacillus subtilis.
abstract: A thermostable variant of the mesophilic xylanase A from Bacillus subtilis (BsXynA-G3_4x) contains the four mutations Gln7His, Gly13Arg, Ser22Pro, and Ser179Cys. The crystal structure of the BsXynA-G3_4x has been solved, and the local environments around each of these positions investigated by molecular dynamics (MD) simulations at 328K and 348K. The structural and MD simulation results were correlated with thermodynamic data of the wild-type enzyme, the 4 single mutants and the BsXynA-G3_4x. This analysis suggests that the overall stabilizing effect is entropic, and is consistent with solvation of charged residues and reduction of main-chain flexibility. Furthermore, increased protein-protein hydrogen bonding and hydrophobic interactions also contribute to stabilize the BsXynA-G3_4x. The study revealed that a combination of several factors is responsible for increased thermostability of the BsXynA-G3_4x; (i) introduction of backbone rigidity in regions of high flexibility, (ii) solvation effects and (iii) hydrophobic contacts.
authors.affiliation: Instituto de Química, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte 59072-970, Brazil.
authors.forename: Sérgio Bergamachi
authors.initials: SB
authors.lastname: Silva
authors.affiliation: Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo 14040-901, Brazil.
authors.forename: Matheus Pinto
authors.initials: MP
authors.lastname: Pinheiro
authors.affiliation: Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo 14040-901, Brazil.
authors.forename: Carlos Alessandro
authors.initials: CA
authors.lastname: Fuzo
authors.affiliation: Instituto de Física, Universidade de São Paulo, São Carlos, São Paulo 13566-590, Brazil.
authors.forename: Samuel Reghim
authors.initials: SR
authors.lastname: Silva
authors.affiliation: Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo 14040-901, Brazil.
authors.forename: Tatiane Lopes
authors.initials: TL
authors.lastname: Ferreira
authors.affiliation: Grupo de modelagem, simulação e evolução in silico de biomoléculas, Fundação Oswaldo Cruz, Fortaleza, Ceará 60.180-900, Brazil; Verdartis Desenvolvimento Biotecnológico Ltda ME, Ribeirão Preto, São Paulo 14.050-410, Brazil.
authors.forename: Marcos Roberto
authors.initials: MR
authors.lastname: Lourenzoni
authors.affiliation: Laboratório de Cristalografia de Proteínas de Ribeirão Preto, Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo 14040-903, Brazil.
authors.forename: M Cristina
authors.initials: MC
authors.lastname: Nonato
authors.affiliation: Instituto de Química, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte 59072-970, Brazil.
authors.forename: Davi Serradella
authors.initials: DS
authors.lastname: Vieira
authors.affiliation: Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo 14040-901, Brazil. Electronic address: rjward@fmrp.usp.br.
authors.forename: Richard John
authors.initials: RJ
authors.lastname: Ward
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology*; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry* / Q000235:genetics*; D004795:Enzyme Stability / Q000235:genetics; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D056004:Molecular Dynamics Simulation; D009154:Mutation; D017433:Protein Structure, Secondary; D013696:Temperature
chemical_list: D043364:Endo-1,4-beta Xylanases
keywords: Backbone rigidity; Crystal structure; Hydrophobic cluster; Molecular dynamics simulation; Solvation effects; Thermodynamic analysis