1932

Abstract

Abstract

An X-ray structure of the lactose permease of (LacY) in an inward-facing conformation has been solved. LacY contains N- and C-terminal domains, each with six transmembrane helices, positioned pseudosymmetrically. Ligand is bound at the apex of a hydrophilic cavity in the approximate middle of the molecule. Residues involved in substrate binding and H+ translocation are aligned parallel to the membrane at the same level and may be exposed to a water-filled cavity in both the inward- and outward-facing conformations, thereby allowing both sugar and H+ release directly into either cavity. These structural features may explain why LacY catalyzes galactoside/H+ symport in both directions utilizing the same residues. A working model for the mechanism is presented that involves alternating access of both the sugar- and H+-binding sites to either side of the membrane.

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/content/journals/10.1146/annurev.biophys.35.040405.102005
2006-06-09
2024-06-21
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  • Article Type: Review Article
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