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A model of maltodextrin transport through the sugar‐specific porin, LamB, based on deletion analysis.
Author(s) -
Klebba P.E.,
Hofnung M.,
Charbit A.
Publication year - 1994
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1994.tb06790.x
Subject(s) - biology , maltodextrin , porin , sugar , food science , biochemistry , escherichia coli , gene , chromatography , bacterial outer membrane , chemistry , spray drying
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.