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Analysis of a sub-proteome which co-purifies with and is phosphorylated by the Golgi casein kinase

Author:
  • E Tibaldi
  • G Arrigoni
  • AM Brunati
  • Peter James
  • LA Pinna
Publishing year: 2006
Language: English
Pages: 378-389
Publication/Series: Cellular and Molecular Life Sciences
Volume: 63
Issue: 3
Document type: Journal article
Publisher: Birkhaüser

Abstract english

In an attempt to gain information about the identity of the Golgi apparatus casein kinase(s) (G-CK), responsible for the phosphorylation of caseins in lactating mammary gland, the proteins present in fractions enriched in G-CK activity eluted from DEAE-Sepharose and heparin-Sepharose columns were resolved by two-dimensional electrophoresis and analyzed by mass spectrometry. This led to the identification of 47 proteins altogether, none of which is a bona fide protein kinase. At least 9 of the identified proteins however, are readily phosphorylated by co-purifying G-CK activity, and 7 are physically associated with it to give supramolecular complex(es) of about 500 kDa as judged from Superdex S200 gel fitration and glycerol gradient ultracentrifugation experiments. In contrast, the apparent molecular weight of G-CK estimated from an in gel activity assay after SDSPAGE and renaturation is about 41 kDa. Many of the proteins phosphorylated by and/or associated with G-CK belong to the category of chaperonines, including HSP90, GRP-94 and -78, and various isoforms of protein disulfide isomerases, suggesting a global role of this kinase in the modulation of protein folding.

Keywords

  • Cell Biology
  • chaperone
  • phosphoprotein
  • staurosporine
  • phosphoproteome
  • mammary gland
  • casein kinase
  • Golgi apparatus

Other

Published
  • ISSN: 1420-9071
Peter James
E-mail: peter.james [at] immun.lth.se

Professor

Department of Immunotechnology

+46 46 222 14 96

+46 70 247 79 60

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