A pivotal role for pro-335 in balancing the dual functions of Munc18-1 domain-3a in regulated exocytosis.

Munc18-1 plays essential dual roles in exocytosis: (i) stabilizing and trafficking the central SNARE protein, syntaxin-1 (i.e. chaperoning function), by its domain-1; and (ii) priming/stimulating exocytosis by its domain-3a.