2v8n

Publication Abstract from PubMed

Here we describe an x-ray structure of wild-type lactose permease (LacY) from Escherichia coli determined by manipulating phospholipid content during crystallization. The structure exhibits the same global fold as the previous x-ray structures of a mutant that binds sugar but cannot catalyze translocation across the membrane. LacY is organized into two six-helix bundles with twofold pseudosymmetry separated by a large interior hydrophilic cavity open only to the cytoplasmic side and containing the side chains important for sugar and H(+) binding. To initiate transport, binding of sugar and/or an H(+) electrochemical gradient increases the probability of opening on the periplasmic side. Because the inward-facing conformation represents the lowest free-energy state, the rate-limiting step for transport may be the conformational change leading to the outward-facing conformation.

Structural determination of wild-type lactose permease.,Guan L, Mirza O, Verner G, Iwata S, Kaback HR Proc Natl Acad Sci U S A. 2007 Sep 25;104(39):15294-8. Epub 2007 Sep 19. PMID:17881559^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.