M1 RNA with large terminal deletions retains its catalytic activity.

Truncated transcripts of the rnpB gene from E. coli, coding for M1 RNA, the catalytic subunit of RNAase P, and fragments of M1 RNA generated by nuclease treatment have been prepared, and their ability to function catalytically in vitro has been determined. Molecules missing as many as 122 nucleotides at the 3' terminus retain catalytic activity, although at a much lower level than M1 RNA itself. No activity is observed with an RNA that is missing 70 nucleotides at the 5' terminus. The removal of even a small number of nucleotides from both termini eliminates all catalytic function. The preservation of one intact terminus may be essential for the tertiary and quaternary interactions required to generate the conformation of an active RNA species.