5EJ1

Pre-translocation state of bacterial cellulose synthase

Summary for 5EJ1

• Entry DOI: 10.2210/pdb5ej1/pdb
• Related: 5EIY
• Descriptor: Putative cellulose synthase, poly(unk), beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose, ... (7 entities in total)
• Functional Keywords: cellulose biosynthesis, glycosyltransferase, membrane transport, metal binding protein
• Biological source: Rhodobacter sphaeroides (strain ATCC 17023 / 2.4.1 / NCIB 8253 / DSM 158); More
• Total number of polymer chains: 3
• Total formula weight: 159693.77

Authors

Moragn, J.L.W.,Zimmer, J. (deposition date: 2015-10-30, release date: 2016-03-30, Last modification date: 2020-07-29)

Primary citation

Morgan, J.L.,McNamara, J.T.,Fischer, M.,Rich, J.,Chen, H.M.,Withers, S.G.,Zimmer, J.
Observing cellulose biosynthesis and membrane translocation in crystallo.
Nature, 531:329-334, 2016

PubMed Abstract: 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. Here, in crystallo enzymology with the catalytically active bacterial cellulose synthase BcsA-BcsB 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.

PubMed: 26958837
DOI: 10.1038/nature16966

Experimental method

X-RAY DIFFRACTION (3.4 Å)