title: Identification of the diacylglycerol kinase structural gene of Rhizobium meliloti 1021.
abstract: The cyclic beta-1,2-glucans of Rhizobium may function during legume nodulation. These molecules may become highly substituted with phosphoglycerol moieties from the head group of phosphatidylglycerol; diglyceride is a by-product of this reaction (K. J. Miller, R. S. Gore, and A. J. Benesi, J. Bacteriol. 170:4569-4575, 1988). We recently reported that R. meliloti 1021 produces a diacylglycerol kinase (EC 2.7.1.107) activity that shares several properties with the diacylglycerol kinase enzyme of Escherichia coli (W. P. Hunt, R. S. Gore, K. J. Miller, Appl. Environ. Microbiol. 57:3645-3647, 1991). A primary function of this rhizobial enzyme is to recycle diglyceride generated during cyclic beta-1,2-glucan biosynthesis. In the present study, we report the cloning and initial characterization of a single-copy gene from R. meliloti 1021 that encodes a diacylglycerol kinase homolog; this homolog can complement a diacylglycerol kinase deficient strain of E. coli. The sequence of the rhizobial diacylglycerol kinase gene was predicted to encode a protein of 137 amino acids; this protein shares 32% identity with the E. coli enzyme. Analysis of hydropathy and the potential to form specific secondary structures indicated a common overall structure for the two enzymes. Because diglyceride metabolism and cyclic beta-1,2-glucan biosynthesis are metabolically linked, future studies with diacylglycerol kinase mutants of R. meliloti 1021 should further elucidate the roles of the cyclic beta-1,2-glucans in the Rhizobium-legume symbiosis.
authors.affiliation: Department of Food Science, Pennsylvania State University, University Park 16802.
authors.forename: K J
authors.initials: KJ
authors.lastname: Miller
authors.forename: M W
authors.initials: MW
authors.lastname: McKinstry
authors.forename: W P
authors.initials: WP
authors.lastname: Hunt
authors.forename: B T
authors.initials: BT
authors.lastname: Nixon
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D019852:Diacylglycerol Kinase; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D010770:Phosphotransferases / Q000235:genetics*; D017434:Protein Structure, Tertiary; D016962:Sinorhizobium meliloti / Q000201:enzymology* / Q000235:genetics*; D013045:Species Specificity
chemical_list: D004269:DNA, Bacterial; D010770:Phosphotransferases; D019852:Diacylglycerol Kinase