National Center for
3ZQW: Structure of CBM3b of major scaffoldin subunit ScaA from Acetivibrio cellulolyticus
Structure of CBM3b of the major cellulosomal scaffoldin subunit ScaA from Acetivibrio cellulolyticus
Acta Crystallogr. Sect. F Struct. Biol. Cryst. Commun. (2012) 68 p.8-13
The carbohydrate-binding module (CBM) of the major scaffoldin subunit ScaA of the cellulosome of Acetivibrio cellulolyticus is classified as a family 3b CBM and binds strongly to cellulose. The CBM3b was overexpressed, purified and crystallized, and its three-dimensional structure was determined. The structure contained a nickel-binding site located at the N-terminal region in addition to a 'classical' CBM3b calcium-binding site. The structure was also determined independently by the SAD method using data collected at the Ni-absorption wavelength of 1.48395 A and even at a wavelength of 0.97625 A in a favourable case. The new scaffoldin-borne CBM3 structure reported here provides clear evidence for the proposition that a family 3b CBM may be accommodated in scaffoldin subunits and functions as the major substrate-binding entity of the cellulosome assembly.