Synhibin: A new calcium‐dependent membrane‐binding protein that inhibits synexin‐induced chromaffin granule aggregation and fusion

We report the isolation and purification of synhibin, a new M r 68000 protein, which inhibits synexin. Synexin mediates Ca 2+ ‐dependent chromaffin granule aggregation and fusion, processes perhaps important during exocytosis. Our data indicate that synhibin action involves competition with synexin for a site on the chromaffin granule membrane involved in membrane contact. Synhibin may thus be an important intracellular regulator of synexin action during secretion.