title: Characterization of the biosynthesis of beta(1-2) cyclic glucan in R. Fredii. Beta(1-2) glucan has no apparent role in nodule invasion of Mc Call and Peking soybean cultivars.
abstract: Three wild type strains of Rhizobium fredii, USDA 191, USDA 257 and HH 303, do not synthesize in vivo or in vitro beta(1-3), beta(1-6) cyclic glucans, all strains form in vitro and in vivo cyclic beta(1-2) glucans. Approximately 80% of the recovered R. fredii cellular cyclic beta(1-2) glucans were anionic and the substituent was identified as phosphoglycerol. Inner membranes prepared from these R. fredii strains have a beta(1-2) glucan-intermediate-protein with apparent molecular mass undistinguishable from Agrobacterium tumefaciens beta(1-2) glucan intermediate protein. Studies of the degree of polymerization of the oligosaccharides recovered from the protein-intermediate after short pulse incubations with UDP-14C-glucose suggested that the rate limiting step in the biosynthesis of cyclic glucan is cyclization. Kinetic studies revealed that the K(m) for UDP-glucose was 0.33 mM. No difference was detected between the K(m) for initiation/elongation and cyclization reactions. Nodulation studies of a ndvB R. fredii mutant with Mc Call and Peking soybean cultivars, revealed that beta(1-2) glucans do not seem to be required for normal nodule invasion of these soybean cultivars.
authors.affiliation: Instituto de Investigaciones Bioquímicas, CONICET, ñó Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
authors.forename: N
authors.initials: N
authors.lastname: Iñón de Iannino
authors.forename: G
authors.initials: G
authors.lastname: Briones
authors.forename: G
authors.initials: G
authors.lastname: Kreiman
authors.forename: R
authors.initials: R
authors.lastname: Ugalde
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification; D005936:Glucans / Q000096:biosynthesis* / Q000737:chemistry; D006020:Glycopeptides / Q000737:chemistry / Q000302:isolation & purification; D007700:Kinetics; D008565:Membrane Proteins / Q000737:chemistry / Q000302:isolation & purification; D008854:Microscopy, Electron; D015394:Molecular Structure; D008970:Molecular Weight; D012231:Rhizobium / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D013025:Glycine max / Q000145:classification / Q000382:microbiology* / Q000648:ultrastructure; D013045:Species Specificity; D013559:Symbiosis; D014532:Uridine Diphosphate Glucose / Q000378:metabolism; D047071:beta-Glucans
chemical_list: D001426:Bacterial Proteins; D005936:Glucans; D006020:Glycopeptides; D008565:Membrane Proteins; D047071:beta-Glucans; C080135:cyclic beta(1-2)glucan; D014532:Uridine Diphosphate Glucose