Open AccessReversal of Rous sarcoma-specific immunoglobulin phosphorylation on tyrosine (ADP as phosphate acceptor) catalyzed by the src gene kinase.
Author(s) -
Yasuo Fukami,
Fritz Lipmann
Publication year - 1983
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.80.7.1872
Subject(s) - tyrosine , phosvitin , chemistry , rous sarcoma virus , proto oncogene tyrosine protein kinase src , phosphate , phosphatase , hydrolysis , protein tyrosine phosphatase , phosphorylation , biochemistry , stereochemistry , protein kinase a , gene
To determine the equilibrium constant of the reaction between ATP and protein-bound tyrosine we used as catalyst the highly purified Rous sarcoma src gene transcript. J. M. Sturtevant had earlier found (personal communication) that free tyrosine O-phosphate, upon hydrolysis with alkaline phosphatase in a calorimeter (37 degrees C, pH 9), yielded a delta H degrees of -2.8 kcal/mol (1 kcal = 4.18 kJ), less than half of that found in ATP hydrolysis. Experience with protein-bound serine phosphate (in phosvitin) had shown it to be energy rich [Rabinowitz, M. & Lipmann, F. (1960) J. Biol. Chem. 235, 1043-1050]. We wondered if the same is true for tyrosine phosphate when it is protein bound. From the equilibrium constant of 2.62 (at pH 6.5 and 5 mM Mg2+), we calculate a delta G degrees' of -9.48 kcal/mol for hydrolysis of protein-bound tyrosine phosphate, assuming an approximate delta G degrees' of -10 kcal/mol for hydrolysis of ATP. The experiments show that protein-bound tyrosine phosphate is energy rich, like serine phosphate in phosvitin.