Abstract
The sequences and structures of RNase P RNAs of some Gram-positive bacteria, e.g. Bacillus subtilis, are very different than those of other bacteria. In order to expand our understanding of the structure and evolution of RNase P RNA in Gram-positive bacteria, gene sequences encoding RNase P RNAs from 10 additional species from this evolutionary group have been determined, doubling the number of sequences available for comparative analysis. The enlarged data set allows refinement of the secondary structure model of these unusual RNase P RNAs and the identification of potential tertiary interactions between P10.1 and L12, and between L5.1 and L15.1. The newly-obtained sequences suggest that RNase P RNA underwent an abrupt, dramatic restructuring in the ancestry of the low-G+C Gram-positive bacteria after the divergence of the branches leading to the 'Clostridia and relatives' and the remaining low-G+C Gram-positive species. The unusual structures of the RNase P RNAs of Mycoplasma hyopneumoniae and M.floccularre are apparently derived from RNAs with Bacillus-like structure rather than from intermediate, partially restructured ancestral RNAs. The structure of the RNase P RNA from the photosynthetic Heliobacillus mobilis supports the relationship of this specie with Bacillus and Staphylococcus rather than the 'Clostridia and relatives' as suggested by the sequences of their small-subunit ribosomal RNAs.