Role of Gly117 in the cation/melibiose symport of MelB of Salmonella typhimurium.

ABSTRACT: The melibiose permease of Salmonella typhimurium (MelB(St)) catalyzes symport of melibiose with Na(+), Li(+), or H(+), and bioinformatics analysis indicates that a conserved Gly117 (helix IV) is part of the Na(+)-binding site. We mutated Gly117 to Ala, Pro, Trp, or Arg; the effects on melibiose transport and binding of cosubstrates depended on the physical-chemical properties of the side chain. Compared with WT MelB(St), the Gly117 → Ala mutant exhibited little difference in either cosubstrate binding or stimulation of melibiose transport by Na(+) or Li(+), but all other mutations reduced melibiose active transport and efflux, and decreased the apparent affinity for Na(+). The bulky Trp at position 117 caused the greatest inhibition of melibiose binding, and Gly117 → Arg yielded less than

SUBMITTER: Guan L 

PROVIDER: S-EPMC3334291 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature