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EMBO J. 1994 Oct 3;13(19):4670-5.

A model of maltodextrin transport through the sugar-specific porin, LamB, based on deletion analysis.

Author information

1
Unité de Programmation Moleculaire et Toxicologie Génétique CNRS URA 1444, Institut Pasteur, Paris, France.

Abstract

LamB facilitates the uptake of maltose and maltodextrins across the bacterial outer membrane and acts as a general porin for small molecules. Using directed deletion mutagenesis we removed several regions of the LamB polypeptide and identified a polypeptide loop that both constricts the maltoporin channel and binds maltodextrins. In conjunction with a second sugar binding site that we identified at the rim of the channel, these data clarify, for the first time, the mechanism of transport through a substrate-specific porin. Furthermore, unlike the transverse loops of general porins, which originate from a central location in their primary structure, the loop that regulates LamB permeability originates from a C-terminal site. Thus LamB represents a second distinct class of porins in the bacterial outer membrane that is differently organized and separately evolved from OmpF-type, general porins.

PMID:
7925308
PMCID:
PMC395401
[Indexed for MEDLINE]
Free PMC Article

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