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Catalytic domain of the atypical protein serine kinase, RIO3 kinase RIO3 is present only in multicellular eukaryotes. It is associated with precursors of 40S ribosomal subunits, just like RIO1 and RIO2. Its specific function is still unknown. Like RIO1 and RIO2, it may be involved in ribosomal subunit processing and maturation. 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. The RIO3 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). |
Jiyao W et al.(2023). "The conserved domain database in 2023.",