4zyr

Publication Abstract from PubMed

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-alpha-d-galactopyranoside (alpha-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 alpha-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.

Structure of LacY with an alpha-substituted galactoside: Connecting the binding site to the protonation site.,Kumar H, Finer-Moore JS, Kaback HR, Stroud RM Proc Natl Acad Sci U S A. 2015 Jul 21;112(29):9004-9. doi:, 10.1073/pnas.1509854112. Epub 2015 Jul 8. PMID:26157133^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.