Membranes of chromaffin granules. Isolation and partial characterization of two proteins

Abstract

Membranes of chromaffin granules were isolated from the adrenal glands of four different species. The solubilized membrane proteins could be resolved into several bands by polyacrylamide-gel electrophoresis (alkaline and acid gel systems). Two major protein components appeared to be common to the chromaffin granule membranes of ox, horse, pig and man. The various membrane proteins of bovine chromaffin granules were separated by filtration on Sephadex G-200 in the presence of sodium dodecyl sulphate. Two major membrane proteins (A and B) were obtained in purified form. Treatment of protein A with 2-mercaptoethanol before electrophoresis resulted in two more rapidly migrating subunits, whereas protein B was unaffected by mercaptoethanol treatment. The amino acid compositions of the two purified proteins were determined. They are very similar to that of the total membrane proteins but significantly different from that of the chromogranins, the soluble proteins of chromaffin granules.

The Proteins of Catecholamine‐storing Organelles

“…The amino acid composition of this protein [75] is given in Table I. It is significantly different from that of chromogranin A.…”

“…Chromomembrin B is a major component of the membranes of chromaffin granules in the low molecular weight region [ll,23a,75,143;see Fig. 11.…”

“…Chromomembrin B was first isolated by Sephadex G-200 chromatography in the presence of I% sodium dodecyl sulphate at room temperature [75]. This detergent solubilizes more than 90% of.…”

Secretion granules of the rabbit parotid gland. Isolation, subfractionation, and characterization of the membrane and content subfractions.

“…Recently, studies performed in three granular systems other than the rabbit parotid--the guinea pig exocrine pancreas, the rat liver, and the bovine adrenal medulla--have given indication that removal of polypeptides known not to be membrane proteins to limiting levels of detectability has not been attained (47,37,26,68,70). In these studies the contaminating proteins are again secretory proteins identified by enzymatic activity, by comparative gel electrophoresis with soluble extracts of the fractions under investigation, or by a characteristic high rate of incorporation of radioactively tagged amino acid during pulse labeling.…”

Monoclonal antibodies to the secretory granule membrane of the rabbit parotid gland: Presence of a common antigen in secretory granules of both exocrine and endocrine cells.

“…However, it remains unknown whether the proteins of the cell membrane translocate from the Golgi complex to cell membrane in association with secretory granules or some other vesicles. Biochemical analysis has revealed that the secretory granule membrane usually had a simpler polypeptide composition on SDS ,-PAGE than that of the cell membrane (1,8,16,26,28,34,38). Recently, Kelly and Moore et al (18,29,31) demostrated two secretory pathways (i,e., "regulated" and "constitutive" pathways) in secretory cells and some cell membrane proteins may be transported from the Golgi trans face to the cell membrane accompanied by small vesicles but not by secretory granules.…”