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- Title
The lactose permease of Escherichia coli: overall structure, the sugar-binding site and the alternating access model for transport
- Authors
Abramson, Jeff; Smirnova, Irina; Kasho, Vladimir; Verner, Gillian; Iwata, So; Kaback, H. Ronald
- Abstract
Membrane transport proteins transduce free energy stored in electrochemical ion gradients into a concentration gradient and are a major class of membrane proteins, many of which play important roles in human health and disease. Recently, the X-ray structure of the Escherichia coli lactose permease (LacY), an intensively studied member of a large group of related membrane transport proteins, was solved at 3.5 A˚. LacY is composed of N- and C-terminal domains, each with six transmembrane helices, symmetrically positioned within the molecule. The structure represents the inward-facing conformation, as evidenced by a large internal hydrophilic cavity open to the cytoplasmic side. The structure with a bound lactose homolog reveals the sugar-binding site in the cavity, and a mechanism for translocation across the membrane is proposed in which the sugar-binding site has alternating accessibility to either side of the membrane.
- Subjects
ESCHERICHIA coli; LACTOSE intolerance; BIOLOGICAL transport
- Publication
FEBS Letters, 2003, Vol 555, Issue 1, p96
- ISSN
0014-5793
- Publication type
Article
- DOI
10.1016/S0014-5793(03)01087-1