Regulation of Phospholipid Synthesis in Escherichia coli by Guanosine Tetraphosphate

Abstract

Phospholipid synthesis has been reported to be subject to stringent control in Escherichia coli . We present evidence that demonstrates a strict correlation between guanosine tetraphosphate accumulation and inhibition of phospholipid synthesis. In vivo experiments designed to examine the pattern of phospholipid labeling with 32 P-inorganic phosphate and 32 P- sn -glycerol-3-phosphate suggest that regulation must occur at the glycerol-3-phosphate acyltransferase step. Assay of phospholipid synthesis by cell-free extracts and semipurified preparations revealed that guanosine tetraphosphate inhibits at least two enzymes specific for the biosynthetic pathway, sn -glycerol-3-phosphate acyltransferase as well as sn -glycerol-3-phosphate phosphatidyl transferase. These findings provide a biochemical basis for the stringent control of lipid synthesis as well as regulation of steady-state levels of phospholipid in growing cells.