An Escherichia coli mutant lacking the cold shock-induced palmitoleoyltransferase of lipid A biosynthesis. Absence of unsaturated acyl chains and antibiotic hypersensitivity at 12 °C

Mara K. Vorachek-Warren, Sherry M. Carty, Shanhua Lin, Robert J. Cotter, Christian R.H. Raetz

Research output: Contribution to journalArticle

Abstract

An acyltransferase induced by cold shock in Escherichia coli, designated LpxP, incorporates a palmitoleoyl moiety into nascent lipid A in place of the secondary laurate chain normally added by LpxL(HtrB) (Carty, S. M., Sreekumar, K. R., and Raetz, C. R. H. (1999) J. Biol. Chem. 274, 9677-9685). To determine whether the palmitoleoyl residue alters the properties of the outer membrane and imparts physiological benefits at low growth temperatures, we constructed a chromosomal insertion mutation in lpxP, the structural gene for the transferase. Membranes from the lpxP, mutant MKV11 grown at 12 °C lacked the cold-induced palmitoleoyltransferase present in membranes of cold-shocked wild type cells but retained normal levels of the constitutive lauroyltransferase encoded by lpxL. When examined by mass spectrometry, about two-thirds of the lipid A molecules isolated from wild type E. coli grown at 12 °C contained palmitoleate in place of laurate, whereas the lipid A of cold-adapted MKV11 contained only laurate in amounts comparable with those seen in wild type cells grown at 30 °C or above. To probe the integrity of the outer membrane, MKV11 and an isogenic wild type strain were grown at 30 or 12 °C and then tested for their susceptibility to antibiotics. MKV11 exhibited a 10-fold increase in sensitivity to rifampicin and vancomycin at 12 °C compared with wild type cells but showed identical resistance when grown at 30 °C. We suggest that the palmitoleoyltransferase may confer a selective advantage upon E. coli cells growing at lower temperatures by making the outer membrane a more effective barrier to harmful chemicals.

Original languageEnglish (US)
Pages (from-to)14186-14193
Number of pages8
JournalJournal of Biological Chemistry
Volume277
Issue number16
DOIs
StatePublished - Apr 19 2002

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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