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Prothymosin α is phosphorylated by casein kinase‐2
Author(s) -
Barcia Miguel G.,
Castro José M.,
Jullien Cristina D.,
González Carlos G.,
Freire Manuel
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)80924-6
Subject(s) - phosphorylation , casein kinase 2 , casein kinase 1 , kinase , biochemistry , peptide sequence , protein phosphorylation , peptide , biology , protein kinase a , microbiology and biotechnology , chemistry , cyclin dependent kinase 2 , gene
Prothymosin α (ProTα) is a 12.5 kDa acidic polypeptide that is considered to have a nuclear function related to cell proliferation. Inspection of its amino acid sequence revealed the presence of sequences that may serve as targets for phosphorylation by casein kinase‐2 (CK‐2). ProTα isolated from calf thymocytes was phosphorylated in vitro by CK‐2. The phosphorylation sites are Ser and Thr residues located among the first 14 amino acid residues in the ProTα sequence. Another site that is theoretically suitable for phosphorylation by CK‐2, at the C‐terminus of the polypeptide, is not, in fact, phosphorylated. Thymosin α 1 (Tα 1 ), a peptide whose sequence corresponds to the first 28 amino acids of ProTα, is also phosphorylated by CK‐2 at the same phosphorylation sites as ProTα. In cultured splenic lymphocytes ProTα was phosphorylated at Thr residues located at positions 7, 12 and/or 13. Based on these observations we conclude that CK‐2, or another cellular kinase with similar sequence specifity, is responsible for phosphorylation of ProTα in vivo.