Serine/threonine protein kinases (EC 184.108.40.206) phosphorylate the OH group of serine or threonine (which have similar sidechains). Activity of these protein kinases can be regulated by specific events (e.g. DNA damage), as well as numerous chemical signals, including:
While serine/threonine kinases all phosphorylate serine or threonine residues in their substrates, they select specific residues to phosphorylate on the basis of residues that flank the phosphoacceptor site, which together comprise the consensus sequence. Since the consensus sequence residues of the substrate to be phosphorylated make contact with the catalytic cleft of the kinase at several key amino acids (usually through hydrophobic forces and ionic bonds), a kinase is usually not specific to a single substrate, but instead can phosphorylate a whole "substrate family" having common recognition sequences. While the catalytic domain of these kinases is highly conserved, the sequence variation that is observed in the kinome (the subset of genes in the genome that encode kinases) provides for recognition of distinct substrates. Most kinases are inhibited by a pseudosubstrate that binds to the kinase like a real substrate but lacks the amino acid to be phosphorylated. When the pseudosubstrate is removed, the kinase can perform its normal function.
Many serine/threonine protein kinases do not have their own individual EC numbers and use "220.127.116.11", which is a general EC number for any enzyme that phosphorylates proteins while converting ATP to ADP (i.e. ATP:protein phosphotransferases.) This category is currently being reviewed by the Nomenclature Committee of IUBMB (NC-IUBMB), and it is believed that the various serine/threonine-kinases will get their own EC numbers eventually.
Pelle is a serine/threonine kinase that can phosphorylate itself, and also Tube and Toll.
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