Identification of a Protein Complex That Assembles Lipopolysaccharide in the Outer Membrane of Escherichia Coli

Overview

Journal Proc Natl Acad Sci U S A

Specialty Science

Date 2006 Jul 25

PMID 16861298

Citations 212

Authors

Tao Wu

Andrew C McCandlish

Luisa S Gronenberg

Shu-Sin Chng

Thomas J Silhavy

Daniel Kahne

Affiliations

Soon will be listed here.

Abstract

The outer membrane of most Gram-negative bacteria is made up of LPS, and in nearly all bacteria that contain LPS it is essential for the life of the organism. The lipid portion of this molecule, lipid A, also known as endotoxin, is a potent activator of the innate immune response. More than 50 genes are required to synthesize LPS and assemble it at the cell surface. Enormous progress has been made in elucidating the structure and biosynthesis of LPS, but until recently the cellular components required for its transport from its site of synthesis in the inner membrane to its final cellular location at the cell surface remained elusive. Here we describe the identification of a protein complex that functions to assemble LPS at the surface of the cell. This complex contains two proteins: Imp, already identified as an essential outer-membrane protein implicated in LPS assembly; and another protein, RlpB, heretofore identified only as a rare lipoprotein. We show that RlpB is also essential for cell viability and that the Imp/RlpB complex is responsible for LPS reaching the outer surface of the outer membrane.

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