4ZYR

Crystal structure of E. coli Lactose permease G46W/G262W bound to p-nitrophenyl alpha-D-galactopyranoside (alpha-NPG)

Summary for 4ZYR

• Entry DOI: 10.2210/pdb4zyr/pdb
• Related: 1PV7 2V8N 2Y5Y 4OAA
• Descriptor: Lactose permease, 4-nitrophenyl alpha-D-galactopyranoside, nonyl beta-D-glucopyranoside (3 entities in total)
• Functional Keywords: membrane protein, transporter, alpha-helical, major facilitator superfamily (mfs), transport protein
• Biological source: Escherichia coli (strain K12)
• Total number of polymer chains: 2
• Total formula weight: 94793.70

Authors

Kumar, H.,Finer-Moore, J.S.,Kaback, H.R.,Stroud, R.M. (deposition date: 2015-05-22, release date: 2015-07-29, Last modification date: 2023-09-27)

Primary citation

Kumar, H.,Finer-Moore, J.S.,Kaback, H.R.,Stroud, R.M.
Structure of LacY with an alpha-substituted galactoside: Connecting the binding site to the protonation site.
Proc.Natl.Acad.Sci.USA, 112:9004-9009, 2015

PubMed Abstract: The X-ray crystal structure of a conformationally constrained mutant of the Escherichia coli lactose permease (the LacY double-Trp mutant Gly-46→Trp/Gly-262→Trp) with bound p-nitrophenyl-α-d-galactopyranoside (α-NPG), a high-affinity lactose analog, is described. With the exception of Glu-126 (helix IV), side chains Trp-151 (helix V), Glu-269 (helix VIII), Arg-144 (helix V), His-322 (helix X), and Asn-272 (helix VIII) interact directly with the galactopyranosyl ring of α-NPG to provide specificity, as indicated by biochemical studies and shown directly by X-ray crystallography. In contrast, Phe-20, Met-23, and Phe-27 (helix I) are within van der Waals distance of the benzyl moiety of the analog and thereby increase binding affinity nonspecifically. Thus, the specificity of LacY for sugar is determined solely by side-chain interactions with the galactopyranosyl ring, whereas affinity is increased by nonspecific hydrophobic interactions with the anomeric substituent.

PubMed: 26157133
DOI: 10.1073/pnas.1509854112

Experimental method

X-RAY DIFFRACTION (3.312 Å)