Protein Phosphorylation

1. Protein Phosphorylation Phosphorylation is the most common and important molecular mechanism of acute and reversible regulation of protein function. Through protein phosphorylation, protein function is regulated in response to extracellular stimuli both inside and outside the cell. Protein phosphorylation is usually analyzed by biosynthetic labeling with 32P-labeled inorganic phosphate (32Pi), and the studies of mammalian cells metabolically labeled with 32P orthophosphate suggest that as many as one-third of all cellular proteins are covalently modified by protein phosphorylation. Most proteins are found to be phosphorylated at serine or threonine residues, and many proteins involved in signal transduction are also phosphorylated at tyrosine residues. Lots of protein kinases exhibit a strict specificity for phosphorylation of either serine/threonine or tyrosine residues. Due to a large number of kinases and phosphatases in the genome, the identification of the specific enzymes responsible for a given site in a given protein is immensely challenging. However, because protein kinases and phosphatases recognize local specificity determinants within proteins, it is possible to use small peptides to study the characteristics of site-specific phosphorylation. In addition, phosphorylation usually causes retardation in gel mobility, providing an opportunity to investigate peptide phosphorylation and de-phosphorylation by monitoring migration on high-resolution peptide gels. Find more: https://www.creative-diagnostics.com/protein-phosphorylation.htm