Poster abstracts
Poster number 65 submitted by Kristin Koutmou
Mechanisms of ribosome stalling during the translation of positively charged peptides
Daniel Eyler (Department of Chemistry, University of Michigan), Alexandra Rizo (Program in Chemical Biology, University of Michigan), Frances Acevedo, Tyler Smith (Department of Chemistry, University of Michigan), Sarah Keane (Department of Chemistry, Department of Biophysics, University of Michigan), Daniel Southworth (University of California San Francisco), Kristin Koutmou (Department of Chemistry, University of Michigan)
Abstract:
The rate that ribosomes catalyze the addition of amino acids as they translate along an mRNA template is highly variable. Changes in translation speed can have far-reaching consequences, affecting mRNA stability, protein folding, and protein subcellular localization. Both biochemical reporter and genome wide ribosome profiling studies indicate that proteins containing iterated positively charged residues are translated slowly, producing transiently arrested ribosome species. While these stalling events are generally thought to occur because positively charged nascent peptide chains form strong ionic interactions with the negatively charged ribosome exit tunnel, there is little direct evidence for this hypothesis. We previously reported that lysine codon usage (AAA vs AAG codons) is a key determinant for how the ribosome translates poly-lysine containing proteins, suggesting that ribosome stalling relies on more than just peptide-ribosome interactions during the translation of some poly-cationic peptides. Here, we take a high-resolution look at the translation of iterated lysine and arginine containing peptides to directly observe if cationic peptide mediated ribosome stalling occurs, and to characterize the mechanism by which the translation of cationic peptides causes translational stalling. Our combination of structural (electron microscopy and NMR) and kinetic data will provide the first measurements of ribosome elongation rates during the synthesis of poly-arginine peptides, and identify contributions of mRNA and ribosome structure to stalling during the translation of positively charged peptides.
Keywords: ribosome, cationic peptide, stalling