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Catalytic domain of Phosphoinositide 3-kinase-related protein kinases PIKK subfamily members include ATM (Ataxia telangiectasia mutated), ATR (Ataxia telangiectasia and Rad3-related), TOR (Target of rapamycin), SMG-1 (Suppressor of morphogenetic effect on genitalia-1), and DNA-PK (DNA-dependent protein kinase). PIKKs have intrinsic serine/threonine kinase activity and are distinguished from other PKs by their unique catalytic domain, similar to that of lipid PI3K, and their large molecular weight (240-470 kDa). They show strong preference for phosphorylating serine/threonine residues followed by a glutamine and are also referred to as (S/T)-Q-directed kinases. They all contain a FATC (FRAP, ATM and TRRAP, C-terminal) domain. PIKKs have diverse functions including cell-cycle checkpoints, genome surveillance, mRNA surveillance, and translation control. The PIKK catalytic domain subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as the typical serine/threonine/tyrosine protein kinases (PKs), aminoglycoside phosphotransferase, choline kinase, and RIO kinases. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",