Biochemical Heterogeneity and Phosphorylation of Coatomer Subunits
The coat protomer complex I (COPI) family of coat proteins are involved in the assembly of membrane-associated coats thought to mediate vesicular transport between the endoplasmic reticulum and the Golgi complex, between adjacent Golgi cisternae, and possibly in the endocytic pathway. We investigate...
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Veröffentlicht in: | The Journal of biological chemistry 1996-03, Vol.271 (12), p.7230-7236 |
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Sprache: | eng |
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Zusammenfassung: | The coat protomer complex I (COPI) family of coat proteins are involved in the assembly of membrane-associated coats thought
to mediate vesicular transport between the endoplasmic reticulum and the Golgi complex, between adjacent Golgi cisternae,
and possibly in the endocytic pathway. We investigated whether this heterogeneity in the sites of COPI action might be reflected
in biochemical heterogeneity of one or more COPI subunits. A simplified method was devised to purify the cytosolic COPI precursor
complex, coatomer, from rat liver cytosol. The individual subunits were analyzed by high resolution two dimensional gel electrophoresis
and mass spectroscopic analysis of tryptic peptides. Considerable charge heterogeneity was observed, particularly for the
β-COP and -COP subunits. The multiple species detected, however, did not appear to reflect the presence of distinct translation products
but rather a significant degree of protein phosphorylation. The observed pI of β-COP was sensitive to alkaline phosphatase
digestion. Moreover, isolation of coatomer from metabolically labeled tissue culture cells demonstrated directly that both
β-COP and -COP, but no other coatomer subunits, were serine-phosphorylated. COPI phosphorylation may regulate coatomer assembly, membrane
recruitment, or the specificity of coatomer-organelle interaction. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.271.12.7230 |