Question12

=Text of the Question:= toc Schrader et al (2011) describes how aminoacyl-tRNA binding to EfTu leads to more uniform translatability. Describe the results of this paper in terms of the kinetic proofreading model we learned in class. Be sure to specify which rate constants go up or down, depending on the tRNA. Add additional steps to the kinetic diagram if necessary.

=Summary of Mechanism= Tightly bound tRNA – increases k1, decreases EFTu/GDP release, decreases peptide bond formation

Weakly bound tRNA – decreases k1, increases EFTu/GDP release, increases peptide bond formation

=Analysis of the Schrader et all (2011):=

=Relevant Literature Figures:=



aa-tRNA tightly bound to EFTu: The fidelity check for these tRNAs is peptide bond formation. Koff decreases and Kon increases. The addition of the ternary complex to the ribosome and the rate of GTP hydrolysis stays the same. KPEP decreases to compensate for the increased Kon. The slow KPEP allows for more time to check if it’s the correct amino acid.

aa-tRNA weakly bound to EFTu: The fidelity check for these tRNAs for these tRNAs is at the first step. Kon decreases and Koff increases. Any incorrect amino acids have more time to be excluded before the ternary complex forms. The rest of the rates are unchanged. The different rates for tRNAs weakly or tightly bound to EFTu leads to more uniform translatability.