ANALYSIS OF THE FUNCTIONAL-ROLE OF CONSERVED RESIDUES IN THE PROTEIN SUBUNIT OF RIBONUCLEASE-P FROM ESCHERICHIA-COLI

The processing of precursor tRNAs and some other small cellular RNAs b y M1 RNA, the catalytic subunit of Escherichia coil ribonuclease P, is accelerated by C5 protein (the protein cofactor) both in vitro and in vivo. In an effort to understand the mechanism by which the protein c ofactor promotes and stabilizes certain conformations of M1 RNA that a re most efficient for RNase P catalysis, we have used site-directed mu tagenesis to generate mutant derivatives of C5 protein and assessed th eir ability to promote RNase P catalysis in vivo and in vitro. Our res ults indicate that certain conserved hydrophobic and basic residues in C5 protein are important for its function and that single amino acid residue changes in C5 protein can alter the substrate specificity of t he RNase P holoenzyme. (C) 1997 Academic Press Limited.