An Asymmetric Conformational Change in LacY.

ABSTRACT: Galactoside/H⁺ symport by the lactose permease of Escherichia coli (LacY) involves reciprocal opening and closing of periplasmic and cytoplasmic cavities so that sugar- and H⁺-binding sites become alternatively accessible to either side of the membrane. After reconstitution into proteoliposomes, LacY with the periplasmic cavity sealed by cross-linking paired-Cys residues does not bind sugar from the periplasmic side. However, reduction of the S-S bond restores opening of the periplasmic cavity and galactoside binding. Furthermore, nanobodies that stabilize the double-Cys mutant in a periplasmic-open conformation and allow free access of galactoside to the binding site do so only after reduction of the S-S bond. In contrast, when cross-linked LacY is solubilized in det

SUBMITTER: Smirnova I 

PROVIDER: S-EPMC5456262 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature