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Ligand-gated diffusion across the bacterial outer membrane.

ABSTRACT: Ligand-gated channels, in which a substrate transport pathway is formed as a result of the binding of a small-molecule chemical messenger, constitute a diverse class of membrane proteins with important functions in prokaryotic and eukaryotic organisms. Despite their widespread nature, no ligand-gated channels have yet been found within the outer membrane (OM) of Gram-negative bacteria. Here we show, using in vivo transport assays, intrinsic tryptophan fluorescence and X-ray crystallography, that high-affinity (submicromolar) substrate binding to the OM long-chain fatty acid transporter FadL from Escherichia coli causes conformational changes in the N terminus that open up a channel for substrate diffusion. The OM long-chain fatty acid transporter FadL from E. coli is a unique paradigm for OM diffusion-driven transport, in which ligand gating within a ?-barrel membrane protein is a prerequisite for channel formation.

SUBMITTER: Lepore BW

PROVIDER: S-EPMC3121852 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature

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Ligand-gated diffusion across the bacterial outer membrane.

Lepore Bryan W BW Indic Mridhu M Pham Hannah H Hearn Elizabeth M EM Patel Dimki R DR van den Berg Bert B

Proceedings of the National Academy of Sciences of the United States of America 20110518 25

Ligand-gated channels, in which a substrate transport pathway is formed as a result of the binding of a small-molecule chemical messenger, constitute a diverse class of membrane proteins with important functions in prokaryotic and eukaryotic organisms. Despite their widespread nature, no ligand-gated channels have yet been found within the outer membrane (OM) of Gram-negative bacteria. Here we show, using in vivo transport assays, intrinsic tryptophan fluorescence and X-ray crystallography, that ...[more]

PMID: 21593406

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