Observing cellulose biosynthesis and membrane translocation in crystallo.
Observing cellulose biosynthesis and membrane translocation in crystallo.
复制标题
DOI：
10.1038/nature16966
复制
发表时间：
2016-03-17
期刊：
影响因子：
64.8
通讯作者：
Zimmer J
中科院分区：
文献类型：
--
作者：
Morgan JL;McNamara JT;Fischer M;Rich J;Chen HM;Withers SG;Zimmer J
Many biopolymers, including polysaccharides, must be translocated across at least one membrane to reach their site of biological function. Cellulose is a linear glucose polymer synthesized and secreted by a membrane-integrated cellulose synthase. In crystallo enzymology with the catalytically-active bacterial cellulose synthase BcsA-B complex reveals structural snapshots of a complete cellulose biosynthesis cycle, from substrate binding to polymer translocation. Substrate and product-bound structures of BcsA provide the basis for substrate recognition and demonstrate the stepwise elongation of cellulose. Furthermore, the structural snapshots show that BcsA translocates cellulose via a ratcheting mechanism involving a “finger helix” that contacts the polymer's terminal glucose. Cooperating with BcsA's gating loop, the finger helix moves ‘up’ and ‘down’ in response to substrate binding and polymer elongation, respectively, thereby pushing the elongated polymer into BcsA’s transmembrane channel. This mechanism is validated experimentally by tethering BcsA's finger helix, which inhibits polymer translocation but not elongation.
