Work

Crystal Structure of a ligand-bound LacY–Nanobody Complex

Year: 2018

Type: article

Abstract: Significance The lactose permease of Escherichia coli (LacY), a model Major Facilitator Superfamily transporter, catalyzes galactoside/H + symport by an alternating access mechanism that involves multiple conformational transitions. Nanobodies (Nbs) generated against a double mutant (LacY WW ) that exists in an outward-open conformation stabilize the periplasmic-open conformer of wild-type LacY, block lactose transport, and lead to a 5–50-fold increase in the on-rate for galactoside binding to WT LacY. The galactoside-binding site in galactoside/LacY ww /Nb9047 is superimposable with other sugar-bound LacY ww structures and therefore is not perturbed due to crystal contacts or nanobody; thus, comparison with apo-LacY ww Nb demonstrates that it most likely represents a transport intermediate primarily seen on the periplasmic side in response to the initial galactoside-binding.

Source: Proceedings of the National Academy of Sciences

DOI: 10.1073/pnas.1801774115