Structure of sugar-bound LacY
Abstract
The lactose permease of Escherichia coli (LacY), a model for the major facilitator superfamily, catalyzes the symport of a galactopyranoside and an H+ across the membrane by a mechanism in which the sugar-binding site in the middle of the protein becomes alternately accessible to either side of the membrane. However, all X-ray structures thus far show LacY in an inward-facing conformation with a tightly sealed periplasmic side. Significantly, by using a double-Trp mutant, we now describe an almost occluded, outward-open conformation with bound sugar, confirming more than two decades of biochemical and biophysical findings. We also present evidence that protonated LacY specifically binds D-galactopyranosides, inducing an occluded state that can open to either side of the membrane.
- Publication:
-
Proceedings of the National Academy of Science
- Pub Date:
- February 2014
- DOI:
- 10.1073/pnas.1324141111
- Bibcode:
- 2014PNAS..111.1784K