ISSN:
1432-0878
Keywords:
Parotid secretory granules
;
Granule membrane proteins
;
Parotid plasma membrane proteins
;
Two-dimensional polyacrylamide gel electrophoresis
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Secretory granules and plasma membranes were isolated from rat parotid cells and characterized enzymatically and by electron microscopy. The proteins of the secretory granule membranes, the secretory granules and the plasma membranes were characterized by two-dimensional polyacrylamide gel electrophoresis and visualized by silver staining. The granule membrane contains 166 polypeptides of which only 26 are also present in the granule contents. The membrane proteins have isoelectric points between 4.75 and 6.45 and apparent molecular weights of 17000 to 190000 Daltons. The granule content proteins are surprisingly complex and contain 122 polypeptides with molecular weights of 11000 to 138000 and isoelectric points of 4.8 to 6.55. Thirteen of these peptides are present as major species. The plasma membrane contains 172 polypeptide species with molecular weights from 17000 to 200000 Daltons and isoelectric points of 5.0 to 6.8. Thirty-five of the plasma membrane proteins are also present in the secretory granule membranes indicating that the two membranes have some enzymatic or structural properties in common. Thus, secretory granule membranes and plasma membranes from parotid cells have a more complex polypeptide composition than has previously been shown for membranes of this type. The systems developed are suitable for the analysis of regulatory events such as protein phosphorylation, proteolytic processing, and other types of post-translational modifications that may be important to the secretory mechanism.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00217404
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