XATR is an alias for the gene, ATR serine/threonine kinase, in humans. Other names include: Serine/threonine-protein kinase ATR; Ataxia telangiectasia and Rad3-related protein; FRAP-related protein 1; Serine/threonine-protein kinase ATR ; MEC1, mitosis entry checkpoint 1, homolog (S. cerevisiae); FCTCS; MEC1; SCKL; SCKL1. The encoded protein is an enzyme with an amino acid length of 2644 and a mass of 301.4 kDa. Other isoforms may exist. XATR is a member of the PI3/PI4-kinase family, ATM subfamily. This gene shares homology with other species, including: Mouse, Rat.