J. Biochem, 1986, Vol. 99, No. 5 1393-1400
© 1986 Japanese Biochemical Society
research-article |
Membrane Phospholipid Synthesis in Escherichia coli: Alteration by Glycerol and Physiological Consequences in a pss Mutant1
*Faculty of Pharmaceutical Sciences, Teikyo University Sagamiko, Kanagawa 199–01
**Department of Biochemistry, Saitama University Urawa, Saitama 338
2 To whom communications should be addressed
Escherichia coli mutants harboring the pss-1 allele (coding for a temperature-sensitive phosphatidylserine synthase) are temperature sensitive for growth and synthesize less phosphatidylethanolamine at higher temperatures, giving rise to abnormal membrane phospholipid compositions. To obtain information concerning the determinant for the phospholipid polar headgroup composition and the lethal factor in the defective membranes, we have examined the effect of increased supply of sn-glycerol 3-phosphate on the phospholipid synthesis and the growth ability of a pss-1 mutant. For this purpose, a pair of E. coli K-12 derivatives isogenic except for the pss-1 allele was constructed from strain BB26-36 to harbor the mutations related to glycerol metabolism (glpD3, glpR2, glpK1, and phoA8). Pulse- and uniform-labeling of phospholipids with 32P at 42
C in a synthetic medium with (0.2%) or without glycerol showed that glycerol further lowered the temperature sensitive formation of phosphatidylethanolamine, removed the phosphatidate and CDP-diacylglycerol accumulated in the absence of glycerol, and resulted in an increase in cardiolipin content in the pss-1 mutant. The phospholipid synthesis and contents in the pss+ strain were not significantly affected by glycerol. Glycerol in the medium markedly enhanced the growth defect of the pss-1 mutant, which was remediable by sucrose. The results indicate that the intracellular pool of sn-glycerol 3-phosphate is the limiting factor for acidic phospholipid synthesis in the pss-1 mutant, and cardiolipin unusually accumulated is injurious to the functional E. coli membranes. Possible determinants for the phospholipid composition of the wild-type E. coli cells are also discussed on the basis of the present observations.
1A part of this work was carried out at the Institute of Applied Microbiology, The University of Tokyo, Buakyo-ku, Tokyo 113. Supported in part by Grants-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan and by Special Coordination Funds for Promoting Science and Technology from the Science and Technology Agency of Japan.