cd05145

RIO kinase family; RIO1, RIO3 and similar proteins, catalytic domain. The RIO kinase catalytic domain family 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 phosphoinositide 3-kinase (PI3K). RIO kinases are atypical protein serine kinases containing a kinase catalytic signature, but otherwise show very little sequence similarity to typical PKs. Serine kinases catalyze the transfer of the gamma-phosphoryl group from ATP to serine residues in protein substrates. The RIO catalytic domain is truncated compared to the catalytic domains of typical PKs, with deletions of the loops responsible for substrate binding. RIO1 is present in archaea, bacteria and eukaryotes. In addition, RIO3 is present in multicellular eukaryotes. RIO1 is essential for survival and is required for 18S rRNA processing, proper cell cycle progression and chromosome maintenance. The biological substrates for RIO1 are unknown. The function of RIO3 is also unknown.