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The phosphorylation of tyrosine residues plays an important role in these two very important processes. Ligand-dependent endocytosis, which is not coupled to secretion, is known to be regulated via tyrosine phosphorylation. The effect of tyrosine phosphorylation is specific to rapid endocytosis.
Tyrosine phosphorylation is a fast, reversible reaction, and one of the major regulatory mechanisms in signal transduction. Cell growth, differentiation, migration, and metabolic homeostasis are cellular processes maintained by tyrosine phosphorylation. The function of protein tyrosine kinases and protein-tyrosine phosphatase counterbalances ...
Tyrosine phosphorylation is considered to be one of the key steps in signal transduction and regulation of enzymatic activity. Phosphotyrosine can be detected through specific antibodies . Tyrosine residues may also be modified by the addition of a sulfate group, a process known as tyrosine sulfation . [ 17 ]
Phosphorylation can occur on serine, threonine and tyrosine side chains (in other words, on their residues) through phosphoester bond formation, on histidine, lysine and arginine through phosphoramidate bonds, and on aspartic acid and glutamic acid through mixed anhydride linkages.
Tyrosine kinases belong to a larger class of enzymes known as protein kinases which also attach phosphates to other amino acids such as serine and threonine. Phosphorylation of proteins by kinases is an important mechanism for communicating signals within a cell (signal transduction) and regulating cellular activity, such as cell division.
The activity of src kinases is regulated by both phosphorylation and intramolecular interactions involving the SH2 and SH3 domains. The probable activation mechanism of src kinase in cancer is as follows: 1. The src kinase is kept in an inactive form through the binding of SH2 to a phosphotyrosine; 2.
Mechanism of Tyrosine dephosphorylation by a CDP. The free cysteine nucleophile forms a bond with the phosphorus atom of the phosphate moiety, and the P-O bond linking the phosphate group to the tyrosine is protonated, either by a suitably positioned acidic amino acid residue (Asp in the diagram below) or a water molecule. The phospho-cysteine ...
Together with tyrosine kinases, PTPs regulate the phosphorylation state of many important signalling molecules, such as the MAP kinase family. PTPs are increasingly viewed as integral components of signal transduction cascades, despite less study and understanding compared to tyrosine kinases.