Fig. 4.

Conversion of NBCe1 into an anion exchanger. a NBCe1 and AE1 amino-acid alignment showing location of the NBCe1 residues replaced with the corresponding AE1 residues. b Location of the NBCe1 residues replaced with the corresponding AE1 residues located in ion coordination site regions of NBCe1 and AE1²² (PDB: 4YZF) formed by antiparallel β-strands preceding TMs 3 and 10, and in TM 8 and 10 are shown. c, e-g Loss of Na⁺-driven base transport and d, h-k  gain of Cl⁻-driven base transport in the mutant constructs. l, m Cell surface expression. Immunoblot analysis of sulfo-NHS-SS-biotin labeled plasma membrane proteins in HEK-293 cells-expressing wt-NBCe1 and NBCe1 mutant (A+B+C). l Cell surface expression was normalized to GAPDH (mutant vs. wt, p < 0.05; one-way ANOVA followed by Tukey’s test). m Immunocytochemistry of HEK-293 cells showing plasma membrane localization of the wt and NBCe1 mutant (A+B+C) transporters, scale bars 5 µm. c, d, l The mean ± s.e.m. is depicted. The number of experiments is shown in parentheses