STIMULATION OF EXOCYTOTIC MEMBRANE-FUSION BY MODIFIED PEPTIDES OF THERAB3 EFFECTOR DOMAIN - REEVALUATION OF THE ROLE OF RAB3 IN REGULATED EXOCYTOSIS

We have shown previously that fusion between pancreatic zymogen granul es and plasma membranes is stimulated by a peptide corresponding to th e putative effector domain of rab3. Here we show that this stimulatory effect persists when the amino acid sequence of the peptide is substa ntially modified. We also show that an antibody raised against rab3a r ecognizes a protein of appropriate size on the zymogen-granule membran e, but has no effect on membrane fusion. We suggest that rab3 is not d irectly involved in the control of this membrane fusion event, and tha t the peptides are stimulating fusion by a mechanism unrelated to rab3 .