Crystal structure of a LacY-nanobody complex in a periplasmic-open conformation.

ABSTRACT: The lactose permease of Escherichia coli (LacY), a dynamic polytopic membrane protein, catalyzes galactoside-H⁺ symport and operates by an alternating access mechanism that exhibits multiple conformations, the distribution of which is altered by sugar binding. We have developed single-domain camelid nanobodies (Nbs) against a mutant in an outward (periplasmic)-open conformation to stabilize this state of the protein. Here we describe an X-ray crystal structure of a complex between a double-Trp mutant (Gly46→Trp/Gly262→Trp) and an Nb in which free access to the sugar-binding site from the periplasmic cavity is observed. The structure confirms biochemical data indicating that the Nb binds stoichiometrically with nanomolar affinity to the periplasmic face of LacY primarily to the C

SUBMITTER: Jiang X 

PROVIDER: S-EPMC5098631 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature