Identification of a second synexin-like adrenal medullary and liver protein that enhances calcium-induced membrane aggregation.

Synexin, an approximately 47,000 Mr soluble protein isolated from adrenal medulla or liver, shows Ca2+-specific enhancement of the aggregation of chromaffin granule or other negatively charged biological or artificial membranes. We report the identification of second synexin-like protein (Mr approximately 56,000) from the same sources with similar Ca2+-specific membrane aggregation activities. However, the molecular weight, aggregation kinetics, susceptibility to protease inactivation and peptide maps of the two synexins are quite different, suggesting that they are entirely different proteins, and that the aggregation assay is only a convenient method for identifying a large number of Ca2+-specific proteins with diverse, yet to be defined activities.