PMID: 21880019

Authors:

Santos C, Paiva J, Sforca M, Neves J, Navarro R, Cota J, Akao P, Hoffmam ZB, Meza A, Smetana J, Nogueira M, Polikarpov I, Xavier-Neto J, Squina F, Ward RJ, Ruller R, Zeri A, Murakami MT

Title:

Dissecting structure-function-stability relationships of a thermostable GH5-CBM3 cellulase from Bacillus subtilis 168.

Journal:

Biochem J. 2011 Sep 1.

Abstract:

Cellulases participate in a number of biological events such as plant cell wall remodeling, nematode parasitism and microbial carbon uptake. Their ability to depolymerize crystalline cellulose is of great biotechnological interest for environmentally-compatible production of fuels from lignocellulosic biomass. However, industrial use of cellulases is somewhat limited both by their low catalytic efficiency and stability. In this work, we conducted a detailed functional and structural characterization of the thermostable cellulase 5A from Bacillus subtilis (BsCel5A), which consists of a GH5 catalytic domain fused to a family 3 carbohydrate-binding module (CBM3). NMR structural analysis revealed that the Bacillus CBM3 represents a new subfamily, which lacks the classical calcium-binding motif and variations in NMR frequencies in the presence of cellopentaose showed the importance of polar residues in the carbohydrate interaction. Together with the catalytic domain, the CBM3 forms a large planar surface for cellulose recognition, which conducts the substrate in a proper conformation to the active site and increases enzymatic efficiency. Notably, the manganese ion demonstrated to have a hyper-stabilizing effect on BsCel5A and by using deletion constructs and X-ray crystallography, we determined that this effect maps to a negatively charged motif located at the opposite face of the catalytic site.