Structural biology of the ribonuclease p in the hyperthermophilic archaeon pyrococcus horikoshii OT3

Pyrococcus horikoshii OT3 is a hyperthermophilic archaeaon -isolated from hydrothermal fluid. Because of their genetic features as well as hyperthermophilic properties, macromolecules produced by this thermophilic bacterium have served as an excellent model for structural biology. Ribonuclease P (RNase P) is a ribonucleoprotein complex involved in the processing of the 5′-leader sequence of precursor tRNA (pre-tRNA). We found that RNase P RNA (PhopRNA) and five proteins in P. horikoshii OT3 reconstituted RNase P activity that exhibited enzymatic properties like those of the authentic enzyme. A mutational analysis indicated that nucleotides A40, A41, and U44 in PhopRNA are crucial for catalysis, strongly suggesting that PhopRNA catalyzes the hydrolysis of pre-tRNA in approximately the same manner as eubacterial RNase P RNAs, even though it has no enzymatic activity in the absence of the proteins. The P. horikoshii RNase P proteins are predominantly involved in optimization of PhopRNA's conformation, though individually they are dispensable for RNase P activity in vitro. This chapter summarizes structure-function relationships of the P. horikoshii RNase P subunits, including the high-resolution structural information that is currently available for the protein subunits.