||Extra tyrosine in the carbohydrate-binding module of Irpex lacteus Xyn10B enhances its cellulose-binding ability
Nishijima, Hiroto ,
Nozaki, Kouichi ,
Mizuno, Masahiro ,
Arai, TsutomuAmano, Yoshihiko
BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY
746 , 2015-05-04 , TAYLOR & FRANCIS LTD , Japan Society for Bioscience, Biotechnology, and Agrochemistry
The xylanase (Xyn10B) that strongly adsorbs on microcrystalline cellulose was isolated from Driselase. The Xyn10B contains a Carbohydrate-binding module family 1 (CBM1) (IrpCBM(Xyn10B)) at N-terminus. The canonical essential aromatic residues required for cellulose binding were conserved in IrpCBM(Xyn10B); however, its adsorption ability was markedly higher than that typically observed for the CBM1 of an endoglucanase from Trametes hirsuta (ThCBMEG1). An analysis of the CBM-GFP fusion proteins revealed that the binding capacity to cellulose (7.8 mu mol/g) and distribution coefficient (2.0L/mu mol) of IrpCBM(Xyn10B)-GFP were twofold higher than those of ThCBMEG1-GFP (3.4 mu mol/g and 1.2L/mu mol, respectively), used as a reference structure. Besides the canonical aromatic residues (W24-Y50-Y51) of typical CBM1-containing proteins, IrpCBM(Xyn10B) had an additional aromatic residue (Y52). The mutation of Y52 to Ser (IrpCBM(Y52S)-GFP) reduced these adsorption parameters to 4.4 mu mol/g and 1.5L/mu mol, which were similar to those of ThCBMEG1-GFP. These results indicate that Y52 plays a crucial role in strong cellulose binding.