Abstract
Monoglucosyldiacylglycerol (MGlcDG) is a minor lipid but known as a precursor of monogalactosyldiacylglycerol, a major glycolipid in cyanobacterial membranes. In a strain Synechocystis sp. PCC 6803, sll1377 encodes MGlcDG synthase which catalyzes a synthesis of MGlcDG from UDP-glucose and diacylglycerol. The enzyme contains 'D, DAD, QXXRW' motif conserved in β-glycosyltransferases. In this study, we conducted site-directed mutagenesis and produced four enzymes in which the conserved motif was changed as follows; D147Q, D200A, R329Q, R331A. The enzymes expressed in E. coli showed very low activity of MGlcDG synthesis in comparison with wild-type enzyme. We also report detailed results of their enzymatic properties. In addition, we will show the correlation between the expression level of sll1377 and the accumulation of MGlcDG in cyanobacteria grown under various stresses.
