Biogenesis of chromaffin granules: incorporation of sulfate into chromogranin B and into a proteoglycan.
The incorporation of [35S]sulfate into the soluble proteins of chromaffin granules was studied. Isolated bovine chromaffin cells were pulse-labeled with [35S]sulfate. The radioactively labeled products were characterized by one- and two-dimensional electrophoresis. Three proteins of chromaffin granules were preferentially labeled. One was identified by immunoprecipitation as chromogranin B (Mr 100,000). This result explains why during cellular synthesis the chromogranin B precursor is converted into a significantly more acidic protein. During chase periods, the newly synthesized chromogranin B was progressively degraded by endogenous proteases. A second labeled protein, much less labeled than chromogranin B, was identified as chromogranin A. The largest portion of the radioactive label was found in a heterogeneous component (Mr 86,000-100,000; pI 4.3-5.0). Digestion experiments with chondroitinase ABC demonstrated that this labeled component and a comigrating Coomassie Blue-stained spot were selectively degraded by this enzyme. This establishes that this component is a proteoglycan.
D000313:Adrenal Medulla / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002810:Chondroitinases and Chondroitin Lyases; D002837:Chromaffin Granules / Q000378:metabolism*; D002838:Chromaffin System / Q000378:metabolism*; D002864:Chromogranins / Q000096:biosynthesis* / Q000302:isolation & purification; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000096:biosynthesis*; D011509:Proteoglycans / Q000096:biosynthesis* / Q000302:isolation & purification; D013431:Sulfates / Q000378:metabolism*; D013462:Sulfur Radioisotopes
D002864:Chromogranins; D009419:Nerve Tissue Proteins; D011509:Proteoglycans; D013431:Sulfates; D013462:Sulfur Radioisotopes; D002810:Chondroitinases and Chondroitin Lyases