Talk abstracts

Talk on Friday 09:50-10:10pm submitted by Lei Sun

Evidence that substrate specific effects of C5 protein lead to uniformity in binding and catalysis by RNase P

Lei Sun (Center for RNA Molecular Biology and Department of Biochemistry, Case Western Reserve University), Frank E. Campbell (Center for RNA Molecular Biology and Department of Biochemistry, Case Western Reserve University), Nathan H. Zahler (Department of Chemistry, The University of Michigan), Michael E. Harris (Center for RNA Molecular Biology and Department of Biochemistry, Case Western Reserve University)

Abstract:
The ribonucleoprotein enzyme RNase P processes all pre-tRNAs, yet some substrates apparently lack consensus elements for recognition. Here, we compare binding affinities and cleavage rates of Escherichia coli pre-tRNAs that exhibit the largest variation from consensus recognition sequences. These results reveal that the affinities of both consensus and non-consensus substrates for the RNase P holoenzyme are essentially uniform. Comparative analyses of pre-tRNA and tRNA binding to the RNase P holoenzyme and P RNA alone reveal differential contributions of the protein subunit to 5¡¯ leader and tRNA affinity. Additionally, these studies reveal that uniform binding results from variations in the energetic contribution of the 5¡¯ leader which serve to compensate for weaker tRNA interactions. Furthermore, kinetic analyses reveal uniformity in the rates of substrate cleavage that result from dramatic (>900-fold) contributions of the protein subunit to catalysis for some non-consensus pre-tRNAs. Together these data suggest that an important biological function of RNase P protein is to offset differences in pre-tRNA structure such that binding and catalysis are uniform.

Keywords: RNase P, C5, RNA