Fig. 3
From: Structural basis for amino acid transport by the CAT family of SLC7 transporters
Functional characterisation of proton coupling residues in GkApcT. a Proton-coupled uptake assays showing that accumulation of l-Ala is driven by an inwardly directed proton electrochemical gradient generated using valinomycin (+v) and an inwardly directed pH gradient (−v). Transport was abolished in the presence of the proton ionophore CCCP. Inset—transport is independent of sodium. b View of Lys191 in the crystal structure, highlighting the interactions made to TMs 1 and 8. The bound l-Ala ligand is shown in magenta. c Mutational analysis of Lys191 using electrogenic and counterflow accumulation of 3H l-Ala. d Mutational analysis of Glu115 and Asp237 using electrogenic and counterflow accumulation assays. n = 3 independent experiments, error bars s.d.
