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Regulation of a rat lung protein tyrosine kinase activity by reversible phosphorylation/dephosphorylation
Author(s) -
Srivastava Ashok K.,
Chiasson Jean-Louis
Publication year - 1988
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(88)80247-3
Subject(s) - phosphorylation , dephosphorylation , protein tyrosine phosphatase , biochemistry , protein phosphorylation , tyrosine , tyrosine phosphorylation , protein kinase a , biology , enzyme , mitogen activated protein kinase kinase , phosphatase , map2k7 , chemistry , microbiology and biotechnology , cyclin dependent kinase 2
Incubation of a partially purified protein tyrosine kinase from rat lung with Mg 2+ and ATP resulted in about 10–15‐fold activation of the enzyme activity as judged by the phosphorylation of poly(Glu:Tyr,4:1), an exogenous substrate. The activation was time dependent and was associated with the phosphorylation of a single protein band of 50 kDa. Phosphoamino acid analysis of the phosphorylated protein indicated that tyrosine was the amino acid being phosphorylated. Upon gel filtration on a Sephacryl S‐200 column, the phosphorylated protein co‐eluted with protein tyrosine kinase and ATP‐binding activities, suggesting that all three activities are part of the same protein. In addition, pretreatment of the partially purified protein tyrosine kinase with alkaline phosphatase inhibited its enzyme activity which could be restored by reincubation with Mg 2+ and ATP. These data suggest that a temporal relationship exists between the phosphorylation and the activation states of rat lung protein tyrosine kinase, and that the phospho‐ and dephospho‐ forms represent the active and inactive (or less active) forms, respectively, of the enzyme.