4OAA

Crystal structure of E. coli lactose permease G46W,G262W bound to sugar

Summary for 4OAA

• Entry DOI: 10.2210/pdb4oaa/pdb
• Related: 1PV7 2V8N 2Y5Y
• Related PRD ID: PRD_900027
• Descriptor: Lactose/galactose transporter, beta-D-galactopyranose-(1-1)-1-thio-beta-D-galactopyranose (2 entities in total)
• Functional Keywords: transmembrane helices helix bundles, sugar transport, symport, major facilitator superfamily, d-galactose d-galactopyranosides, transport protein
• Biological source: Escherichia coli
• Total number of polymer chains: 2
• Total formula weight: 94295.14

Authors

Kumar, H.,Kasho, V.,Smirnova, I.,Finer-Moore, J.,Kaback, H.R.,Stroud, R.M. (deposition date: 2014-01-03, release date: 2014-01-29, Last modification date: 2023-09-20)

Primary citation

Kumar, H.,Kasho, V.,Smirnova, I.,Finer-Moore, J.S.,Kaback, H.R.,Stroud, R.M.
Structure of sugar-bound LacY.
Proc.Natl.Acad.Sci.USA, 111:1784-1788, 2014

PubMed Abstract: Here we describe the X-ray crystal structure of a double-Trp mutant (Gly46→Trp/Gly262→Trp) of the lactose permease of Escherichia coli (LacY) with a bound, high-affinity lactose analog. Although thought to be arrested in an open-outward conformation, the structure is almost occluded and is partially open to the periplasmic side; the cytoplasmic side is tightly sealed. Surprisingly, the opening on the periplasmic side is sufficiently narrow that sugar cannot get in or out of the binding site. Clearly defined density for a bound sugar is observed at the apex of the almost occluded cavity in the middle of the protein, and the side chains shown to ligate the galactopyranoside strongly confirm more than two decades of biochemical and spectroscopic findings. Comparison of the current structure with a previous structure of LacY with a covalently bound inactivator suggests that the galactopyranoside must be fully ligated to induce an occluded conformation. We conclude that protonated LacY binds D-galactopyranosides specifically, inducing an occluded state that can open to either side of the membrane.

PubMed: 24453216
DOI: 10.1073/pnas.1324141111

Experimental method

X-RAY DIFFRACTION (3.5 Å)