Chk1 (human, recombinant)

Checkpoint kinase 1 (Chk1) is a serine/threonine kinase and downstream effector of ataxia-telangiectasia and RAD3-related protein/kinase (ATR) in the cellular DNA damage response. It is composed of an N-terminal kinase domain, a flexible linker region, a serine/glutamine cluster, and a C-terminal regulatory domain, which contains two conserved motifs, CM1 and CM2, that mediate kinase autoinhibition. Chk1 is ubiquitously expressed and localized primarily to the nucleus. In response to single-stranded DNA (ssDNA) generated from replication stress, DNA crosslinking, or other damage, ATR phosphorylates Chk1 at serine 345 and 317 inducing its activation and cell cycle arrest at the S or G2/M phase. Loss of one copy of Chek1 induces erythropoietic defects, anemia, and sudden death in mice, while Chek1 knockout is embryonically lethal. Pharmacologic inhibition of Chk1 increases DNA damage and enhances antitumor efficacy of chemotherapeutic agents in various mouse xenograft models. Cayman's Chk1 (human, recombinant) protein can be used for enzyme activity assay and Western blot (WB) applications. This protein has a calculated molecular weight of 59 kDa.