Data are presented as mean ± SD except for the ΔF/F versus voltage relationship of Anap, for which data are presented as mean ± SEM. Data analyses were performed using Microsoft Excel 2016, PatchMaster, Clampfit (Molecular Devices), and Igor Pro software. Statistical tests were conducted using Microsoft Excel 2016 and R statistical software.
The phosphatase activity of VSP was taken as the rate constant, which was determined by fitting of a normalized Kir current decay with a single exponential function (21 (link)–23 (link, no link found)) (SI Appendix, Fig. S1 A and B ). QOFF-V curves and F-V curves of G214C* mutants were fitted with the Boltzmann equation: Q(V)/Qmax or F(V)/Fmax = 1/{1 + exp[−(V − V1/2)/β]}, where β is the slope factor and V1/2 is the half-maximum potential at which Q(V) = Qmax/2 or F(V) = Fmax/2. β is expressed as β = kT/ze0, where k is the Boltzmann’s constant, T is the absolute temperature, z is the effective valence, and e0 is the elementary charge. In some mutants where the QOFF did not clearly saturate within the experimental voltage range, the fitting of QOFF-V curves was performed on the stipulation that 0 < Q(V) < 1.
The phosphatase activity of VSP was taken as the rate constant, which was determined by fitting of a normalized Kir current decay with a single exponential function (21 (link)–
