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Title: A model of maltodextrin transport through the sugar-specific porin, LamB, based on deletion analysis. Author: Klebba PE, Hofnung M, Charbit A. Journal: EMBO J; 1994 Oct 03; 13(19):4670-5. PubMed ID: 7925308. 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.[Abstract] [Full Text] [Related] [New Search]