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Structural determination of wild-type lactose permease.

ABSTRACT: 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.

SUBMITTER: Guan L

PROVIDER: S-EPMC2000551 | biostudies-literature | 2007 Sep

REPOSITORIES: biostudies-literature

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Structural determination of wild-type lactose permease.

Guan Lan L Mirza Osman O Verner Gillian G Iwata So S Kaback H Ronald HR

Proceedings of the National Academy of Sciences of the United States of America 20070919 39

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 t ...[more]

PMID: 17881559

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Lactose Permease Scrambles Phospholipids.

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