CLONING AND CHARACTERIZATION OF THE RNASE P-RNA GENES FROM 2 PORCINE MYCOPLASMAS

We report the cloning of the RNase P RNA genes from the primary aetiol ogical agent of porcine pneumonia, Mycoplasma hyopneumoniae, and the c losely related commensal, Mycoplasma flocculare. The monocistronic gen es each have promoters with AT-rich -35 regions and Rho-independent-li ke transcription terminators which are retained in the RNase P RNA. Bo th of these RNase P RNA variants are shown to be catalytically active in vitro in spite of a low overall GC content (30%). Our results sugge st a new example of a stable mini-helix in the conserved core of the m ycoplasmal RNase P RNAs. Deletion of the corresponding structural elem ent in Escherichia coil RNase P RNA (Mi RNA) generated an RNase P RNA with an impaired substrate interaction. Displacement of this structura l element with the mycoplasmal mini-helix resulted in an enzyme with a phenotype similar to that of wild-type M1 RNA. In addition, this stru ctural element is important for lead ion-induced cleavage at specific sites in M1 RNA.