Biosynthesis of cyclic β-(1,2)-glucans in Rhizobium leguminosarum biovars viciae, phaseoli and trifolii

Inner membranes of Rhizobium leguminosarum biovars viciae, phaseoli, and trifolii synthesized a heterogenous family of neutral cyclic β-(1,2)-glucans in a reaction system that used oligosaccharide intermediates covalently bound to a large protein. This glucoprotein showed a slightly lower mobility on SDS-polyacrylamide gels (apparent mol. mass of 320 kDa) than the β-(1,2)-glucan intermediate protein of Rhizobium meliloti. In vivo pulse-label experiments with growing cells of R. leguminosarum biovar trifolii RS800 using radioactive glucose showed that few species of cyclic β-(1,2)-glucans were synthesized and up to 30% were substituted with charged non-glycosidic residues, probably sn-1-phosphoglycerol.