Figure 5.

Kinetics of transmitter release in neurons expressing synaptotagmin I mutants. A, Normalized plots of cumulative charge released from the knock-out neurons transfected with the indicated synaptotagmin I mutants. Data are presented as in Figure 2 B, and double exponential functions are fit to the data. Data for knock-out neurons expressing wild-type synaptotagmin I (dashed line) are replotted from Figure 2 B for comparison. The number of replicates for each mutant are as follows: eight for D1N, five for D2N, five for D3N, six for D4N, and seven for D5N. B, C, Time constants (B) and relative amplitudes (C) of the fast synchronous (left) and slow asynchronous (right) components of transmitter release from knock-out neurons transfected with either wild-type (Stg I) or mutant (D1N-D5N) synaptotagmin I. The values are means ± SEM and were calculated by double exponential fitting of results obtained from individual cells. Asterisks indicate differences that are significantly different from those obtained from cells transfected with wild-type synaptotagmin I.