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If the archaeal RNase P RNAs look like bacterial RNAs, and like them also have catalytic activity in the absence of protein, can we reconstitute a functional holoenzyme from the archaeal RNAs and a bacterial RNase P protein? Yes, we can. In this gel you can see that the E. coli RNase P RNA can cleave substrate under "physiological conditions" in the absence of protein (or with a non-specific protein, bovine serum albumin), but this activity is greatly enhanced by the addition of the the RNase P protein from the bacterium B. subtilis. The RNase P RNAs of methanobacteria (M. formicicum and M.thermoautotrophicus) by themselves are completely dead under these conditions, but the B. subtilis RNase P protein activates cleavage by the RNA; in other words, the archaeal RNAs can productively bind to the protein, reconstituting a functional chimeric holoenzyme.

Notice that the Haloferax RNA also responds to the bacterial RNase P protein, as originally reported by the Daniels lab, but in our hands this is a mis-cleavage; this phenomenon remains to be characterized.