Xenopus oocyte expression of hAE1 wild-type (wtAE1), the AE1 R760Q mutant and the AE double mutant E681Q–R760Q. (a) cation influx: (i) Li+ and (ii) Rb+ influx, measured as previously reported (Guizouarn et al. 2001, 2007) (b) AE1 anion exchange function assessed by intracellular pH measurements, performed as previously reported (Guizouarn et al. 2007). (i) wt hAE1, (ii) R760Q, (iii) E681Q–R760Q. NI denotes non-injected oocytes.