title: 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 β-barrel membrane protein is a prerequisite for channel formation.
authors: University of Massachusetts Medical School, Program in Molecular Medicine, 373 Plantation Street, Worcester, MA 01605, USA.
authors: Bryan W
authors: BW
authors: Lepore
authors: Mridhu
authors: M
authors: Indic
authors: Hannah
authors: H
authors: Pham
authors: Elizabeth M
authors: EM
authors: Hearn
authors: Dimki R
authors: DR
authors: Patel
authors: Bert
authors: B
authors: van den Berg
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