Particular Effects of Genistein on Tyrosine Phosphorylation of Maize Mitochondrial Proteins

Abstract

The activity of specific tyrosine protein kinases is known to be associated with the production of oncogenes. A specific inhibitor of tyrosine protein kinases can be effective not only as an antitumor agent but also as a tool for studying the physiological role of tyrosine phosphorylation. Among similar inhibitors, the flavonoid genistein was shown to have the most specific effect. This agent almost completely inhibited phosphorylation of tyrosine residues, while the activity of serine and threonine protein kinases was slightly suppressed. At the same time, another flavonoid quercetin inhibited activities of tyrosine kinase and other protein kinases with equal efficacy. The aim of the work was to study the effect of genistein on phosphorylation of maize mitochondrial proteins at the tyrosine residues for the assessment of signal cascades associated with tyrosine protein kinases. It was first revealed that tyrosine phosphorylation occurred in the maize mitochondrial heat shock protein 60 (HSP60) and the protein of 90 kDa. Phosphorylation of the 90-kDa protein is observed only during the treatment of isolated mitochondria with genistein. The study of the activity of mitochondrial respiratory complex V showed a significant decrease in the hydrolytic activity of the mitochondrial ATPase after exposure to genistein. The activating effect of this agent on mitochondrial protein kinases can be explained by changes in the redox state of mitochondria due to inhibition of mitochondrial ATPase by genistein.