Yaniv Oren, Halfon Yehuda, Shimon Linda J W, Bayer Edward A, Lamed Raphael, Frolow Felix
Department of Molecular Microbiology and Biotechnology, Tel Aviv University, 69978 Tel Aviv, Israel.
Acta Crystallogr Sect F Struct Biol Cryst Commun. 2012 Jan 1;68(Pt 1):8-13. doi: 10.1107/S174430911104807X. Epub 2011 Dec 24.
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 Å and even at a wavelength of 0.97625 Å 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.
解纤维醋弧菌纤维小体的主要支架蛋白亚基ScaA的碳水化合物结合模块（CBM）被归类为3b家族CBM，它与纤维素紧密结合。对CBM3b进行了过表达、纯化和结晶，并确定了其三维结构。该结构除了含有一个“经典”的CBM3b钙结合位点外，在N端区域还含有一个镍结合位点。在有利的情况下，还使用在1.48395 Å的镍吸收波长甚至0.97625 Å波长处收集的数据，通过SAD方法独立确定了该结构。本文报道的新的支架蛋白携带的CBM3结构为以下观点提供了明确证据：3b家族CBM可能存在于支架蛋白亚基中，并作为纤维小体组装的主要底物结合实体发挥作用。
