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Catalytic domain of Ataxia telangiectasia and Rad3-related proteins ATR is also referred to as Mei-41 (Drosophila), Esr1/Mec1p (Saccharomyces cerevisiae), Rad3 (Schizosaccharomyces pombe), and FRAP-related protein (human). ATR contains a UME domain of unknown function, a FAT (FRAP, ATM and TRRAP) domain, a catalytic domain, and a FATC domain at the C-terminus. Together with its downstream effector kinase, Chk1, ATR plays a central role in regulating the replication checkpoint. ATR stabilizes replication forks by promoting the association of DNA polymerases with the fork. Preventing fork collapse is essential in preserving genomic integrity. ATR also plays a role in normal cell growth and in response to DNA damage. ATR is a member of the phosphoinositide 3-kinase-related protein kinase (PIKK) subfamily. 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). The ATR 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.
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