Regulation of diacylglycerol kinase biosynthesis in Escherichia coli. A trans-acting dgkR mutation increases transcription of the structural gene.

The mechanism of a trans-acting mutation, dgkR1, which causes a 7-fold elevation of diacylglycerol kinase activity in membranes (Raetz, C. R. H., Kantor, G. D., Nishijima, M., and Jones, M. L. (1981) J. Biol. Chem. 256, 2109-2112) was investigated by direct measurement of diacylglycerol kinase polypeptide by high performance liquid chromatography and by construction of fusions of the dgkA promoter to beta-galactosidase and galactokinase. The dgkR1 mutation was demonstrated to act by increasing the transcription of the structural gene for diacylglycerol kinase, dgkA. Additionally, sn-glycerol-3-phosphate acyltransferase activities were shown to be decreased 30-50% in membranes from dgkR1 mutant strains. Increased diacylglycerol levels occurred when cells were grown on low osmolarity media. This did not affect dgkA expression. In a dgkR+ background, enhanced expression of sn-1,2-diacylglycerol kinase activity in cells containing a high copy number plasmid bearing dgkA decreased sn-1,2-diacylglycerol levels. However, overproduction of diacylglycerol kinase in a dgkR1 genetic background did not affect diacylglycerol levels, suggesting that the dgkR1 mutation affects diacylglycerol metabolism by mechanisms additional to enhancement of dgkA transcription.