Involvement of YkoN in production of a new phospholipid in Bacillus subtilis Marburg

To understand the physiological role of the ykoN gene of Bacillus subtilis, the gene was expressed from the IPTG-inducible spac promoter in B. subtilis cells. When lipid composition of the cells induced for ykoN expression was examined, a new spot of phospholipid was found on the thin layer chromatogram. Induction of ykoN in Escherichia coli cells produced a similar new spot. The new spot was produced in mutant E. coli cells lacking cardiolipin or phosphatidylethanolamine, but not in the cells lacking phosphatidylglycerol. The result suggests an involvement of phosphatidylglycerol in production of the new spot. Examination of the lipid composition during the stages of B. subtilis growth revealed that the new phospholipid was produced four hours after cessation of logarithmic growth, consistent with an increase in the promoter activity of ykoN in the late stage in sporulation. YkoN has the pentapeptide lipase/esterase motif (Gly-X-Ser-X-Gly), and shows a lipolytic activity (Matsuura et al., in press). The mutant YkoN (S205A) in which the central serine residue of the motif is replaced with alanine produced the new phospholipid in the amount as small as only 1/10 of the wild type, suggesting that the lipolytic activity of YkoN is involved in the new phospholipid production.