Characterization of the two-protein complex in Escherichia coli responsible for lipopolysaccharide assembly at the outer membrane

Shu Sin Chng, Natividad Ruiz, Gitanjali Chimalakonda, Thomas J. Silhavy, Daniel Kahne

Research output: Contribution to journalArticle

133 Scopus citations

Abstract

Lipopolysaccharide (LPS) is the major glycolipid that is present in the outer membranes (OMs) of most Gram-negative bacteria. LPS molecules are assembled with divalent metal cations in the outer leaflet of the OM to form an impervious layer that prevents toxic compounds from entering the cell. For most Gram-negative bacteria, LPS is essential for growth. In Escherichia coli, eight essential proteins have been identified to function in the proper assembly of LPS following its biosynthesis. This assembly process involves release of LPS from the inner membrane (IM), transport across the periplasm, and insertion into the outer leaflet of the OM. Here,we describe the biochemical characterization of the two-protein complex consisting of LptD and LptE that is responsible for the assembly of LPS at the cell surface. We can overexpress and purify LptD and LptE as a stable complex in a 1:1 stoichiometry. LptD contains a soluble N-terminal domain and a C-terminal transmembrane domain. LptE stabilizes LptD by interacting strongly with the C-terminal domain of LptD. We also demonstrate that LptE binds LPS specifically and may serve as a substrate recognition site at the OM.

Original languageEnglish (US)
Pages (from-to)5363-5368
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume107
Issue number12
DOIs
StatePublished - Mar 23 2010

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Gram-negative bacteria
  • Lipopolysaccharide binding
  • Outer membrane protein complex

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