Bacterial lipid synthesizing enzymes PlsY and PlsC utilize both stereo-forms of glycerol-phosphate

The chemical composition of membrane lipids differs between eukarya, bacteria and archaea. The central dogma posits that the stereochemistry of phospholipids in bacteria is distinct from archaea. Bacterial phospholipids consist of fatty acid lipid tails esterified to the sn-glycerol 3-phosphate lipid backbone (G3P), whereas archaeal phospholipids comprise isoprenoid lipid tails ether-linked to the stereochemical different sn-glycerol 1-phosphate (G1P). This segregation, the “lipid divide”, is however not as strict as previously thought. Recent reports demonstrate that both glycerol-phosphate backbones are present in phospholipids from various Gram-positive bacteria. To test if the stereochemical variability can be attributed to conventional lipid biosynthesis, we characterize the stereospecificity of the relevant glycerol-phosphate acyltransferases PlsY and PlsB, as well as the lysophosphatidic acid acyltransferase PlsC, catalyzing the key steps in phospholipid biosynthesis yielding phosphatidic acid, both in the Gram-positive B. subtilis and the Gram-negative E. coli. While PlsB is strictly stereospecific for glycerol 3-phosphate, PlsY and PlsC can utilize both stereo-forms of the glycerol-phosphate. Hence, the variability in lipid backbone stereochemistry is an intrinsic part of bacterial phospholipid biogenesis, questioning the supposedly strict stereochemical segregation of bacteria and archaea after the lipid divide.