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Unphosphorylated α‐PKC exhibits phorbol ester binding but lacks protein kinase activity in vitro
Author(s) -
Filipuzzi Ireos,
Fabbro Doriano,
Imber Roland
Publication year - 1993
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.240520111
Subject(s) - protein kinase c , phosphorylation , biochemistry , enzyme , protein kinase a , kinase , threonine , chemistry , microbiology and biotechnology , biology , serine
Expression of the α‐isoform of protein kinase C (α‐PKC) in E. coli yielded the unphosphorylated 74 kD precursor molecule. This precursor form exhibited phospholipid‐ and calcium‐dependent phorbol ester binding but lacked, in contrast to the phosphorylated enzyme, protein kinase activity. In addition, the precursor molecule was found to interact with both threonine and an ATP analogon, which demonstrates that phosphorylation of α‐PKC is not required for binding of substrates, cofactors, or activators. These results, therefore, suggest that posttranslational phosphorylation of α‐PKC is not needed for the formation of a functional enzyme‐substrate complex but is necessary for the catalytic transfer of phosphate residues from ATP to protein substrates.