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Biogenesis of Chromaffin Granules: Incorporation of Sulfate into Chromogranin B and into a Proteoglycan
Author(s) -
Falkensammer G.,
FischerColbrie R.,
Winkler H.
Publication year - 1985
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1985.tb07215.x
Subject(s) - chromogranin a , proteoglycan , biochemistry , chemistry , immunoprecipitation , proteolysis , biogenesis , gel electrophoresis , proteases , microbiology and biotechnology , enzyme , biology , extracellular matrix , immunohistochemistry , gene , immunology
The incorporation of [ 35 S]sulfate into the soluble proteins of chromaffin granules was studied. Isolated bovine chromaffin cells were pulse‐labeled with [ 35 S]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 (M r 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 (M r 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.