Human Catecholamine Storage Vesicle Proteins

Abstract

Catecholamines in the adrenal medulla and sympathetic nerve are stored in vesicles, along with numerous proteins and peptides; both catecholamines and proteins are released by and are markers of exocytosis during sympathoadrenal neurosecretion. The proteins include the enzyme dopamine-β-hydroxylase and the chromogranins, a group of molecules of largely undetermined function. We have isolated catecholamine storage vesicles (chromaffin granules) from bovine adrenal medulla and human pheochromocytoma. The numerous soluble proteins in the granules: (a) have a spectrum of sizes; (b) have a spectrum of charges; and (c) display considerable interspecies qualitative homology. Dopamine-β-hydroxylase (DBH) was isolated from human and bovine vesicles by Concanavalin A affinity chromotography. DBH is a tetrameric glycoprotein consisting of 2 non-covalently joined dimeric subunits, each of which is 2 disulfide linked monomers; interspecies molecular weight differences were noted. Ongoing studies concern chromogranin A, the quantitatively major vesicle protein, in bovine and human vesicles.