Nora Inion de Iannino, Gabriel Briones, Gabriel Kreiman, Rodolfo Ugalde

Characterization of the Biosynthesis of betha(1-2) Cyclic Glucan in R. Fredii. betha(1-2) Glucan has no Apparent Role in Nodule Invasion of McCall and Peking Soybean Cultivars

Cellular and Molecular Biology (1996) 42:617-629 PDF

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Three wild type strains of Rhizobium fredii, USDA 191, USDA 257 and HH 303, do not synthesize in vivo or in vitro b (1-3), b (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 b (1-2) glucans were anionic and the substituent was identified as phosphoglycerol. Inner membranes prepared from these R.fredii strains have a b (1-2) glucan-intermediate-protein with apparent molecular mass undistinguishable from Agrobacterium tumefaciens b (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-C-14-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 Me Call and Peking soybean cultivars, revealed that b (1-2) glucans do not seem to be required for normal nodule invasion of these soybean cultivars.