Abstract:
:Protein ubiquitination plays an important role in ATP-dependent protein turnover, and it also may regulate other cellular events. Covalent attachment of ubiquitin to other proteins is catalyzed by three different enzymes, E1, E2, and E3. We have previously shown that protein ubiquitination can be regulated by phosphorylation. In the present study, we show that 20-kDa E2, an E2 molecular mass isoform, is phosphorylated by a protein kinase from the cytosolic fraction of HeLa cells. This protein kinase was purified by a procedure involving ammonium sulfate precipitation and three column chromatographies (phenyl-Sepharose, Superose gel filtration, and DEAE-Sephacel). Gel-filtration chromatography indicated that the molecular mass of this protein kinase was about 300 kDa. However, SDS/PAGE showed that the purified protein kinase consists of three subunits with molecular masses of 120, 105, and 70 kDa, respectively. The stoichiometry of the phosphorylated 20-kDa E2 isozyme was found to be 0.45 mol of phosphate per mol of protein. The phosphorylation of 20-kDa E2 occurred only at the serine residue. The activity of this protein kinase required the presence of Mg2+; however, the enzyme was inhibited by a high concentration of Mg2+.
journal_name
Proc Natl Acad Sci U S Aauthors
Kong SK,Chock PBdoi
10.1073/pnas.91.24.11601subject
Has Abstractpub_date
1994-11-22 00:00:00pages
11601-5issue
24eissn
0027-8424issn
1091-6490journal_volume
91pub_type
杂志文章abstract::In order to retain in an in situ system the control mechanisms involved in synthesis of bacteriophage T4 DNA, infected cells were made permeable to nucleotides by plasmolysis with concentrated sucrose. Such preparations use exogenous deoxyribonucleotides to synthesize T4 phage DNA. As has been observed with in vivo st...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
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更新日期:2004-03-02 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
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更新日期:2000-10-10 00:00:00
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journal_title:Proceedings of the National Academy of Sciences of the United States of America
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更新日期:1976-11-01 00:00:00