The RNase P RNAs from Methanococcus and Archaeoglobus lack secondary structural features essential for the recognition of pre-tRNA. In the absence of protein, these RNase P RNAs lack catalytic activity. How the Methanococcus and Archaeoglobus RNase P holoenzymes compensate for the absent RNA structural elements is not known, but we hypothesize that it is via additional proteins. The Methanococcus jannaschii RNase P holoenzyme has been purified for structural and functional characterization. This enzyme has a buoyant density in Cs2SO4 of 1.39 g/ml and an apparent molecular weight of greater than 400kDa. The holoenzyme has a Km of 68 nM, a kcat of 37nM min-1 (similar to that of other RNase P enzymes) and tolerates a wide range of ionic conditions. Six potential protein subunits have been identified on the basis of copurification with enzymatic activity. The molecular weight of three of these bands is consistent with apparent holomologs of RNase P proteins from Methanobacterium thermoautotrophicum and Saccharomyces cerevisiae.
