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Quelle: Wikipedia Serine-threonine-specific protein kinase 2006 Seite(n): 1 (online source), Zeilen: - |
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| 1) Serine/threonine-specific protein kinases
Serine/threonine protein kinases phosphorylate the -OH group of serine or threonine (which has similar sidechains). Activity of these protein kinases can be regulated by specific events (e.g. DNA damage), as well as numerous chemical signals, including cAMP/cGMP, diacylglycerol, and Ca2+/calmodulin. These kinases are not specific to a similar consensus sequence - that is there is no common "target sequence" to be phosphorylated. Since the substrate to be phosphorylated aligns with the kinase by several key amino acids (usually through hydrophopic forces and ionic bonds), a kinase is usually specific, not to a single substrate, but to a whole "substrate family" having common properties. The kinases are usually inactivated by a pseudosubstrate that binds to the kinase like a real substrate but lacks the amino acid to be phosphorylated. Its removal activates the kinase. The catalytic domain of these kinases is highly conserved. - Phosphorylase kinase: phosphorylase kinase was the first Ser/Thr protein kinase to be discovered (Krebs EG et al., (1959) J Biol Chem). - Protein kinase A: protein kinase A consists of two domains, a small domain with several β sheet structures and a larger domain containing several α helices. The binding sites for substrate and ATP are located in the catalytic cleft between the domains (or lobes). When ATP and substrate bind, the two lobes rotate so that the terminal phosphate group of the ATP and the target amino acid of the substrate move into the correct positions for the catalytic reaction to take place. |
Serine/threonine-specific protein kinase
[...] Serine/threonine protein kinases (EC 2.7.11.1) 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. [...] Phosphorylase kinase Phosphorylase kinase (EC 2.7.11.19) was in fact, the first Ser/Thr protein kinase to be discovered (in 1959 by Krebs et al.). Protein kinase A [...] Protein kinase A (EC 2.7.11.1) consists of two domains, a small domain with several β sheet structures and a larger domain containing several α helices. The binding sites for substrate and ATP are located in the catalytic cleft between the domains (or lobes). When ATP and substrate bind, the two lobes rotate so that the terminal phosphate group of the ATP and the target amino acid of the substrate move into the correct positions for the catalytic reaction to take place. |
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