A Chlamydia trachomatis UDP-N-acetylglucosamine acyltransferase selective for myristoyl-acyl carrier protein: Expression in Escherichia coli and formation of hybrid lipid A species

Charles R. Sweet, Shanhua Lin, Robert J. Cotter, Christian R.H. Raetz

Research output: Contribution to journalArticle

Abstract

Chlamydia trachomatis lipid A is unusual in that it is acylated with myristoyl chains at the glucosamine 3 and 3′ positions. We have cloned and expressed the gene encoding UDP-N. acetylglucosamine 3-O-acyltransferase of C. trachomatis (CtlpxA), the first enzyme of lipid A biosynthesis. C. trachomatis LpxA displays ∼20-fold selectivity for myristoyl-ACP over R/S-3-hydroxymyristoyl-ACP under standard assay conditions, consistent with the proposed structure of C. trachomatis lipid A. CtLpxA is the first reported UDP-N-acetylglucosamine acyltransferase that prefers a non-hydroxylated acyl-ACP to a hydroxyacyl-ACP. When CtlpxA was expressed in R0138, a temperature-sensitive lpxA mutant of Escherichia coli, five new hybrid lipid A species were made in vivo after 2 h at 42 °C, in place of Escherichia coli lipid A. These compounds were purified and analyzed by matrix-assisted laser desorption ionization/time of flight mass spectrometry. In each case, a myristoyl chain replaced one or both of the ester linked 3-hydroxymyristoyl residues of E. coli lipid A. With prolonged growth at 42 °C, all the ester-linked 3-hydroxymyristoyl residues were replaced with myristate chains. Re-engineering the structure of E. coli lipid A should facilitate the microbiological production of novel agonists or antagonists of the innate immunity receptor TLR-4, with possible uses as adjuvants or anti-inflammatory agents.

Original languageEnglish (US)
Pages (from-to)19565-19574
Number of pages10
JournalJournal of Biological Chemistry
Volume276
Issue number22
DOIs
StatePublished - Jun 1 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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