Structure and mechanism of the lactose permease of Escherichia coli
| Autor: | H. Ronald Kaback, So Iwata, G. Verner, Irina Smirnova, Jeff Abramson, Vladimir N. Kasho |
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| Rok vydání: | 2003 |
| Předmět: |
Lactose permease
Models Molecular Monosaccharide Transport Proteins Stereochemistry Protein Conformation Lactose Crystallography X-Ray Beta-galactoside permease Protein Structure Secondary Substrate Specificity Thiogalactosides Protein structure Escherichia coli Ion transporter Multidisciplinary Binding Sites Ion Transport biology Symporters Membrane transport protein Permease Escherichia coli Proteins Cell Membrane Membrane Transport Proteins Biological Transport Hydrogen Bonding Membrane transport Major facilitator superfamily Protein Structure Tertiary Amino Acid Substitution Mutation biology.protein Protons Crystallization Hydrophobic and Hydrophilic Interactions |
| Zdroj: | Science (New York, N.Y.). 301(5633) |
| ISSN: | 1095-9203 |
| Popis: | Membrane transport proteins that transduce free energy stored in electrochemical ion gradients into a concentration gradient are a major class of membrane proteins. We report the crystal structure at 3.5 angstroms of the Escherichia coli lactose permease, an intensively studied member of the major facilitator superfamily of transporters. The molecule is composed of N- and C-terminal domains, each with six transmembrane helices, symmetrically positioned within the permease. A large internal hydrophilic cavity open to the cytoplasmic side represents the inward-facing conformation of the transporter. The structure with a bound lactose homolog, β-D-galactopyranosyl-1-thio-β-D-galactopyranoside, reveals the sugar-binding site in the cavity, and residues that play major roles in substrate recognition and proton translocation are identified. We propose a possible mechanism for lactose/proton symport (co-transport) consistent with both the structure and a large body of experimental data. |
| Databáze: | OpenAIRE |
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