※ RIO family introduction

    RIO family belongs to atypical protein kinase group, which share little similarity of high kinase domain with ePK. RIO family is present in organisms varying from archaea to humans. All these organisms contain at least two RIO proteins, Rio1 and Rio2, but a third Rio3 group is present in multicellular eukaryotes. Rio1 and Rio2 possess kinase activity which has been demonstrated shown to be essential in S. cerevisiae and required for proper cell cycle progression and chromosome maintenance (1).

Reference
1. LaRonde-LeBlanc, N. and Wlodawer, A. (2005) The RIO kinases: an atypical protein kinase family required for ribosome biogenesis and cell cycle progression. Biochim Biophys Acta, 1754, 14-24. PMID: 16182620