Figure 3.

Effects of mutations in the P protein on T. maritima RNase P activity. P protein variants with single-alanine exchanges were examined under single-turnover enzyme conditions and classified according to their effect on RNase P activity: wt-like (green), modest (cyan), substantial (blue) and severe (dark magenta) activity defects, as detailed in Figure 2. The results indicate that the protein residues showing the most severe reduction in activity are located far from the active site and contact the N₋₄ and N₋₅ phosphates of the leader. Single-nucleotide and amino acid exchanges that comprise the dm U52C RNA/F17A protein or U52C RNA/R89A protein RNase P holoenzymes are depicted by red asterisks. A relative activity scale classifies each mutant (as previously colour coded) into the various subgroups based on single-turnover enzyme kinetics. The dm RNase P holoenzyme mutants (red) exhibits a >210-fold decrease in activity compared with the T. maritima holoenzyme and are significantly less active than the wild-type P RNA ribozyme under high salt (magenta, hs) conditions.