we suggest that synexin exists as a soluble monomer in the cytoplasm of the resting chromaffin cell and that when the cell is stimulated to secrete , the increase in the intracellular concentrations of ca2+ causes synexin to form rods , similar to those formed in vitro , which bind to chromaffin granule and plasma membranes , joining them together to form the `` '' pentalaminar '' '' fusion complexes characteristic of the first step in exocytosis .
C0007634
cell
C0007603
plasma membranes