Identification of the cellulose-binding domain of the cellulosome subunit S1 from Clostridium thermocellum YS

Abstract

The 3′ region of a gene designated cipB, which shows strong homology with cipA that encodes the cellulosome S_L subunit of Clostridium thermocellum ATCC 27405, was isolated from a gene library of C. thermocellum strain YS. The truncated S1 protein encoded by the cipB derivative bound tightly to cellulose. The cellulose-binding domain in this polypeptide consisted of a C-terminal proximal 167 residue sequence which showed complete identity with residues 337–503 of mature S_L from C. thermocellum strain ATCC 27405. The cellulose-binding domain interacted with both crystalline and amorphous cellulose, but not with xylan.