Diacylglycerol kinases (DG kinases) catalyze the ATP-dependent phosphorylation of sn-l,2-diacylglycerols. Escherichia coli DG kinase functions to recycle diacylglycerol (DAG), which is generated largely as a by-product of membrane-derived oligosaccharide biosynthesis. Recent observations with mutants defective in the regulation of DG kinase expression suggest that DAG may play a regulatory role in E. coli analogous to its role in eukaryotic signal transduction. Diacylglycerol kinase from E. coli has found use in a radiochemical assay of DAG levels in crude lipid extracts of eukaryotic cells. The structural gene for E. coli DG kinase has been cloned and its DNA sequence determined. Bacterial strains expressing high levels of enzyme activity have been constructed and employed for purifying the enzyme to homogeneity. Sequence analysis of the purified kinase has allowed alignment of the protein with the structural gene. Kinetic analyses indicate that in addition to MgATP and diacylglycerol, E. coli DG kinase requires a second divalent metal cation and a lipid cofactor. Several lines of kinetic evidence suggest that the lipid cofactor induces a conformational change in the enzyme prior to its interaction with DAG, MgATP, and the divalent metal activator.
ASJC Scopus subject areas
- Molecular Biology