Lactose permease
| LacY proton/sugar symporter | |||||||||
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Crystal Structure of Lactose Permease in Complex with an Affinity Inactivator. PDB 2y5y
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| Identifiers | |||||||||
| Symbol | LacY_symp | ||||||||
| Pfam | PF01306 | ||||||||
| Pfam clan | CL0015 | ||||||||
| InterPro | IPR022814 | ||||||||
| PROSITE | PDOC00698 | ||||||||
| TCDB | 2.A.1 | ||||||||
| OPM superfamily | 15 | ||||||||
| OPM protein | 2cfq | ||||||||
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| Available protein structures: | |
|---|---|
| Pfam | structures |
| PDB | RCSB PDB; PDBe; PDBj |
| PDBsum | structure summary |
Lactose permease is a membrane protein which is a member of the major facilitator superfamily. Lactose permease can be classified as a symporter, which uses the proton gradient towards the cell to transport β-galactosides such as lactose in the same direction into the cell.
The protein has twelve transmembrane helices and exhibits an internal two-fold symmetry, relating the N-terminal six helices onto the C-terminal helices. It is encoded by the lacY gene in the lac operon.
The sugar lies in a pocket in the center of the protein which is accessible from the periplasm. On binding, a large conformational change takes place which makes the sugar binding site accessible from the cytoplasm.
Mechanism: hydrogen from the outside of the cell binds to a carboxyl group on the enzyme that allows it to undergo a conformational change. This form of lactose permease can bind lactose from outside the cell. The enzyme then everts and lactose is transported inward.
The X-ray crystal structure was first solved in 2003 by J. Abramson et al.
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