PMID:7925308

Citation	Klebba, PE, Hofnung, M and Charbit, A (1994) A model of maltodextrin transport through the sugar-specific porin, LamB, based on deletion analysis. EMBO J. 13:4670-5
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.
Links	PubMed PMC395401
Keywords	Amino Acid Sequence; Bacterial Outer Membrane Proteins; Binding Sites; Escherichia coli/metabolism; Maltose/metabolism; Models, Biological; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Polysaccharides/metabolism; Porins/metabolism; Protein Conformation; Receptors, Virus/metabolism
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