Table 1.

Kinetic properties of PM H⁺-ATPase mutants

PM H+-ATPase	Specific activity (µmol/mg/min)	pH optimum	ATP affinity, Km (µM)	Vanadate inhibition, IC50 (µM)	Proton transport, + valinomycin (%)	Proton transport, − valinomycin (%)
Wild type	25.7 ± 1.8	∼6.8	45 ± 5	∼8	100	100
R456V	0.7 ± 0.1	< 5.6*	1428 ± 69	∼39	n.d.†	n.d.†
D92A	11.8 ± 2.9	∼6.6 - 6.8	36 ± 6	∼7 - 8	24.7 ± 10.3	7.3 ± 1.9
D95A	16.7 ± 0.5	∼6.8	39 ± 4	∼6	37.6 ± 4.0	17.3 ± 3.6
D92A,D95A	12.4 ± 1.3	∼6.6 - 6.8	35 ± 13	∼16	18.2 ± 1.0	5.3 ± 0.2

^*The pH optimum was not determined within the tested range but appears to be shifted toward more acidic values (Fig. S5B).

^†n.d., not determined.