Fig. 4.

Functional coupling of the enzymatic domain to the VSD is mediated by the PBM. A: Critical basic residues (red) are conserved between the PBMs of Ci-VSP and hVSP1. Asterisks indicate positions mutated to glutamine or alanine. B: Charge-neutralizing mutations K252Q and R253Q in the PBM of hVSP1 greatly reduce voltage-dependent activation of hVSP1_CiV. Experiments were performed as in (Fig 1A, B), and data from cells expressing wt hVSP1_CiV are replotted from Fig. 1B for comparison. Depolarization to 80 mV is indicated by shaded area [N = 8 (K252Q) or 9 (R253Q) cells]. C: Average depolarization-activated enzymatic activity for the PBM mutants indicated. Activity is quantified as the degree of dissociation of PH_PLCδ1-GFP from the membrane, measured as in B.