J. Biol. Chem., Vol. 261, Issue 15, 6651-6653, 05, 1986
Evidence of the activity of tyrosine kinase(s) and of the presence of phosphotyrosine proteins in pea plantlets
M Torruella, LM Casano and RH Vallejos
Homogenate fractions from etiolated pea plantlets showed tyrosine kinase
activity when incubated with [32P]ATP and substrates like polyamino acid
polymer (Glu-Ala-Tyr)n or [Val5]angiotensin II. When these tyrosine kinase
substrates were recovered by high voltage electrophoresis, and analyzed by
high pressure liquid chromatography after alkaline hydrolysis, yielded
radioactive phosphotyrosine. The same product was obtained after acid
hydrolysis of either endogenous or exogenous substrates. Phosphorylated
polypeptides were extracted after sodium dodecyl sulfate gel
electrophoresis of a pellet fraction incubated with [32P]ATP. After acid
hydrolysis and high voltage electrophoresis, [32P]phosphotyrosine was found
in gel bands with polypeptides of about 92 and 57 kDa. These results
suggest that tyrosine kinase(s) and phosphotyrosine proteins are also
present in higher plants.