Ribonuclease P (RNase P) and ribosome are the only two naturally occurring ribozymes that are present in all three kingdoms of life. RNase P is an ancient ribonucleoprotein (RNP) complex that catalyzes the maturation of the 5′ end of precursor tRNAs (pre-tRNAs). Bacterial RNase P is composed of a single small RNase P protein (RPP) in addition to the RNase P RNA (RPR). Based on the secondary structures, bacterial RPRs have been further classified into two subtypes, the most common type A for ancestral and type B for Bacillus5. Structural information of both bacterial A-type and B-type RPRs reveals that RPR consists of two independently folded domains, the catalytic domain (C-domain) and the specificity domain (S-domain), which play key roles in substrate cleavage and substrate binding, respectively. In contrast to bacteria, archaeal and eukaryal nuclear RNase Ps have evolved considerably more complex protein subunits, four to five in archaeal and nine to ten in eukaryal enzymes. Archaeal RNase P is an evolutionary intermediate with chimeric features of both bacterial and eukaryal nuclear enzymes, and thus serves as an excellent system to provide insights into the structural and functional alterations that accompanied the gradual transformation of an ancient catalytic RNA to a protein-rich RNP. Here you can see the cryo-EM structure of an archaeal Ribonuclease P (PDB code: 6K0A)

#molecularart ... #immolecular ... #ribonuclease ... #archaea ... #evolution ... #cryoem

Structure rendered with @proteinimaging and depicted with @corelphotopaint