title: Cellulose Microfibril Formation by Surface-Tethered Cellulose Synthase Enzymes.
abstract: Cellulose microfibrils are pseudocrystalline arrays of cellulose chains that are synthesized by cellulose synthases. The enzymes are organized into large membrane-embedded complexes in which each enzyme likely synthesizes and secretes a β-(1→4) glucan. The relationship between the organization of the enzymes in these complexes and cellulose crystallization has not been explored. To better understand this relationship, we used atomic force microscopy to visualize cellulose microfibril formation from nickel-film-immobilized bacterial cellulose synthase enzymes (BcsA-Bs), which in standard solution only form amorphous cellulose from monomeric BcsA-B complexes. Fourier transform infrared spectroscopy and X-ray diffraction techniques show that surface-tethered BcsA-Bs synthesize highly crystalline cellulose II in the presence of UDP-Glc, the allosteric activator cyclic-di-GMP, as well as magnesium. The cellulose II cross section/diameter and the crystal size and crystallinity depend on the surface density of tethered enzymes as well as the overall concentration of substrates. Our results provide the correlation between cellulose microfibril formation and the spatial organization of cellulose synthases.
authors.affiliation: Department of Agricultural and Biological Engineering, Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Snehasish
authors.initials: S
authors.lastname: Basu
authors.affiliation: Center for Membrane Biology, Department of Molecular Physiology and Biological Physics, University of Virginia , Charlottesville, Virginia 22908, United States.
authors.forename: Okako
authors.initials: O
authors.lastname: Omadjela
authors.affiliation: Department of Electrical Engineering, Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: David
authors.initials: D
authors.lastname: Gaddes
authors.affiliation: Department of Electrical Engineering, Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Srinivas
authors.initials: S
authors.lastname: Tadigadapa
authors.affiliation: Center for Membrane Biology, Department of Molecular Physiology and Biological Physics, University of Virginia , Charlottesville, Virginia 22908, United States.
authors.forename: Jochen
authors.initials: J
authors.lastname: Zimmer
authors.affiliation: Department of Agricultural and Biological Engineering, Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Catchmark
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D019149:Bioreactors; D044602:Cellulases; D002482:Cellulose / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism*; D005964:Glucosyltransferases / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D004800:Enzymes, Immobilized; D002482:Cellulose; D005964:Glucosyltransferases; C478648:cellulose synthase; D044602:Cellulases
keywords: BcsA-B cellulose synthase; allomorph; cellulose biosynthesis; cellulose microfibril synthesis and assembly; crystal size; crystallinity; surface immobilization