Article
- The EMBO Journal (2006) 25, 1177 - 1183
- doi:10.1038/sj.emboj.7601028
Published online: 9 March 2006
Subject Categories:
Structural evidence for induced fit and a mechanism for sugar/H+ symport in LacY
Osman Mirza2,3,4, Lan Guan1,3, Gill Verner1, So Iwata2 and H Ronald Kaback1,4
- Department of Physiology and Microbiology, Immunology & Molecular Genetics, Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA, USA
- Department of Biological Sciences, Membrane Protein Crystallography Group, Imperial College London, London, UK
- These authors contributed equally to this work
- Current address: Biostructural Research, Department of Medicinal Chemistry, The Danish University of Pharmaceutical Sciences, Copenhagen 2100, Denmark
Correspondence to:
H Ronald Kaback, Department of Physiology and Microbiology, Immunology & Molecular Genetics, Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA 90095-1662, USA. Tel.: +1 310 206 5053; Fax: +1 310 206 8623; E-mail: rkaback@mednet.ucla.edu
So Iwata, Department of Biological Sciences, Membrane Protein Crystallography Group, Imperial College London, London SW7 2AZ, UK. E-mail: s.iwata@imperial.ac.uk
Received 9 January 2006; Accepted 8 February 2006
Abstract
Cation-coupled active transport is an essential cellular process found ubiquitously in all living organisms. Here, we present two novel ligand-free X-ray structures of the lactose permease (LacY) of Escherichia coli determined at acidic and neutral pH, and propose a model for the mechanism of coupling between lactose and H+ translocation. No sugar-binding site is observed in the absence of ligand, and deprotonation of the key residue Glu269 is associated with ligand binding. Thus, substrate induces formation of the sugar-binding site, as well as the initial step in H+ transduction.
Keywords:
- bioenergetics,
- coupling,
- membrane proteins,
- transport
