mEPSC recorded in HEK cells cultured with Syb2/cellubrevin knockout neurons transfected with WT-Syb2 and two Syb2 tryptophan TMD mutants. (A) Average of HEK cell mEPSCs with neurons expressing WT Syb2 (Syb2WT) and a Syb2 double mutant with tryptophan at positions 101 and 103 (2W). (B–E) Plots of amplitude (B), area (C), rise rate (D), and decay time (E) for the indicated mutants. Cell means ± standard errors with cell numbers in the amplitude bars of B. For rise rate (D), P = 0.0021 for 101W versus WT and 0.0057 for 2W versus WT. For decay (E), P = 0.003 for 101W versus WT and 0.00014 for 2W versus WT. **, P < 0.01; ***, P < 0.001.