title: Crystallographic snapshot of cellulose synthesis and membrane translocation.
abstract: Cellulose, the most abundant biological macromolecule, is an extracellular, linear polymer of glucose molecules. It represents an essential component of plant cell walls but is also found in algae and bacteria. In bacteria, cellulose production frequently correlates with the formation of biofilms, a sessile, multicellular growth form. Cellulose synthesis and transport across the inner bacterial membrane is mediated by a complex of the membrane-integrated catalytic BcsA subunit and the membrane-anchored, periplasmic BcsB protein. Here we present the crystal structure of a complex of BcsA and BcsB from Rhodobacter sphaeroides containing a translocating polysaccharide. The structure of the BcsA-BcsB translocation intermediate reveals the architecture of the cellulose synthase, demonstrates how BcsA forms a cellulose-conducting channel, and suggests a model for the coupling of cellulose synthesis and translocation in which the nascent polysaccharide is extended by one glucose molecule at a time.
authors.affiliation: Center for Membrane Biology, Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, USA.
authors.forename: Jacob L W
authors.initials: JL
authors.lastname: Morgan
authors.forename: Joanna
authors.initials: J
authors.lastname: Strumillo
authors.forename: Jochen
authors.initials: J
authors.lastname: Zimmer
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D055162:Biocatalysis; D001692:Biological Transport; D020134:Catalytic Domain; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D002482:Cellulose / Q000096:biosynthesis / Q000378:metabolism*; D018360:Crystallography, X-Ray; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016992:Rhodobacter / Q000737:chemistry* / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D046912:Multiprotein Complexes; D011134:Polysaccharides; C062025:bis(3',5')-cyclic diguanylic acid; D002482:Cellulose; D006152:Cyclic GMP