Tyrosine -specific protein kinase

The growth requirement for EGF is a good example in this regard. EGF stimulates the growth of many different types of animal cells in culture. In order to initiate the growth response, EGF interacts with specific EGF receptors localized in the plasma membrane, activating a tyrosine-specific protein kinase, which is an intrinsic part of the receptor (Figure 12). As a consequence, specific proteins are phosphorylated at tyrosine residues, and some of these proteins (which are also... 

Genistein, a specific inhibitor of tyrosine-specific protein kinases. JBiol Chem. 262 5592-5. 

It is not clear whether V(V) or V(IV) (or both) is the active insulin-mimetic redox state of vanadium. In the body, endogenous reducing agents such as glutathione and ascorbic acid may inhibit the oxidation of V(IV). The mechanism of action of insulin mimetics is unclear. Insulin receptors are membrane-spanning tyrosine-specific protein kinases activated by insulin on the extracellular side to catalyze intracellular protein tyrosine phosphorylation. Vanadates can act as phosphate analogs, and there is evidence for potent inhibition of phosphotyrosine phosphatases (526). Peroxovanadate complexes, for example, can induce autophosphorylation at tyrosine residues and inhibit the insulin-receptor-associated phosphotyrosine phosphatase, and these in turn activate insulin-receptor kinase. 

Studies similar to the substrate specificity studies outlined for oAMP-dependent protein kinase have already begun for other protein kinases such as cGMP-dependent protein kinase ( ), phos-jAiorylase kinase (69-71) and two tyrosine-specific protein kinases (72-75). 

Akiyama, T., Ishida, J., Nakagawa, S., Ogawara, H., Watanabe, S., Itoh, N., Shibuya, M., and Eukami, Y., Genistein, a specific inhibitor of tyrosine-specific protein kinases, J. Biol. Chem., 262, 5592, 1987. 

Starting from the activated receptor, a large number of reactions can be set in motion (Fig. 5.5). One main route of signal transmission takes place by activation of G-prote-ins, another via activation of tyrosine-specific protein kinases, and a further route is via activation of ion chaimels. In the further course of G-protein mediated signal transmis-... 

Signal Transmission via Transmembrane Receptors with Tyrosine-specific Protein Kinase Activity... 

Receptor tyrosine kinases possess binding sites at the surface of the cell membrane that are specific for extracellular ligands. Ligand binding to the receptor activates a tyrosine-specific protein kinase activity of the receptor, located on the cytoplasmic domain. Consequently, tyrosine phosphorylation is initiated, at the receptor itself and also on substrate proteins these in turn trigger the biological response of the cell by... 

In addition to receptor tyrosine kinases, the cell also contains a number of tyrosine-specific protein kinases that are not an integral component of transmembrane receptors. These nonreceptor tyrosine kinases are localized in the cytoplasm at least occasionally or they are associated with transmembrane receptors on the cytoplasmic side of the cell membrane. They are therefore also known as cytoplasmic tyrosine kinases. The nonreceptor tyrosine kinases perform essential functions in signal transduction via cytokine receptors (see Chapter 11) and T cell receptors, and in other signaling pathways. 

The Insulin Receptor Is a Tyrosine-Specific Protein Kinase... 

FIGURE 26-31 Rous sarcoma vims genome. The src gene encodes a tyrosine-specific protein kinase, one of a class of enzymes known to function in systems that affect cell division, cell-cell interactions, and intercellular communication (Chapter 12). The same gene is found in... 

This part is a tyrosine-specific protein kinase... 

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