Conformation analysis of a surface loop that controls active site access in the GH11 xylanase A from Bacillus subtilis

Autor(es)

Vieira, Davi Serradella ^[1] ; Ward, Richard John ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Dept Quim, Fac Filosofia Ciencias & Letras Ribeirao Preto, BR-1404090 Ribeirao Preto, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Molecular Modeling; v. 18, n. 4, p. 1473-1479, APR 2012.
• Citações Web of Science: 8

Resumo

Xylanases (EC 3.2.1.8 endo-1,4-glycosyl hydrolase) catalyze the hydrolysis of xylan, an abundant hemicellulose of plant cell walls. Access to the catalytic site of GH11 xylanases is regulated by movement of a short beta-hairpin, the so-called thumb region, which can adopt open or closed conformations. A crystallographic study has shown that the D11F/R122D mutant of the GH11 xylanase A from Bacillus subtilis (BsXA) displays a stable ``open{''} conformation, and here we report a molecular dynamics simulation study comparing this mutant with the native enzyme over a range of temperatures. The mutant open conformation was stable at 300 and 328 K, however it showed a transition to the closed state at 338 K. Analysis of dihedral angles identified thumb region residues Y113 and T123 as key hinge points which determine the open-closed transition at 338 K. Although the D11F/R122D mutations result in a reduction in local inter-intramolecular hydrogen bonding, the global energies of the open and closed conformations in the native enzyme are equivalent, suggesting that the two conformations are equally accessible. These results indicate that the thumb region shows a broader degree of energetically permissible conformations which regulate the access to the active site region. The R122D mutation contributes to the stability of the open conformation, but is not essential for thumb dynamics, i.e., the wild type enzyme can also adapt to the open conformation. (AU)

• Processo FAPESP: 09/50838-5 - Determinantes de estabilidade estrutural de enzimas xilanases termofílicas mutantes por dinâmica molecular: efeitos da glicosilação sobre a termoestabilidade
• Beneficiário: Davi Serradella Vieira
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado