YerQ is a soluble diacylglycerol kinase in Bacillus subtilis required for lipoteichoic acid synthesis

Abstract

The biosynthesis of lipoteichoic acid in Gram-positive bacteria involves the sequential transfer of multiple glycerophosphate units from phosphatidylglycerol to the glycolipid anchor with the concomitant release of sn-1,2-diacylglycerol (DAG). DAG is reintroduced into the phospholipid biosynthetic pathway by DAG kinase. This reaction is carried out by an integral membrane protein encoded by the dgkA gene in E. coli; however, the related dgkA gene of Bacillus subtilis was not a DAG kinase. There are three B. subtilis genes, yerQ, bmrU and ytlR, that belong to the DAG kinase protein family established based on the similarities between the soluble mammalian DAG kinases (Pfam00781). Only yerQ complemented the DAG kinase deficiency in the E. coli dgkA mutant. YerQ was essential in B. subtilis and a conditional yerQ knockout strain was constructed that expressed yerQ under the control of the Pspac promoter. Removal of the inducer resulted in the cessation of growth, the accumulation of DAG, a reduction in the levels of phosphatidylglycerol and lysylphosphatidylglycerol, and the termination of lipoteichoic acid formation. YerQ was purified and possessed ATP:Mg2+-dependent DAG kinase activity in vitro. Thus, B. subtilis has a soluble DAG kinase that is more closely related to the mammalian DAG kinase catalytic cores than to the prototypical, membrane-bound E. coli DgkA.