CDF is reduced by disruption of the IS6-AID linker and loss of Ca_Vβ binding. (A) Relative current increase between the last (40th) and first +20-mV pulses at 3 Hz for Ca_V1.2 and the indicated mutants. Parentheses indicate the number of oocytes tested. Results of unpaired t tests are indicated as follows: N.S., P > 0.05, not significant; ***, P < 0.001. (B) Exemplar current traces for Ca_V1.2 I1624A, Ca_V1.2 GGG/I1624A, and Ca_V1.2 HotA/I1624A in a 3-Hz 40-pulse train normalized to the peak of the first pulse.