Our research is directed towards understanding the mechanisms that determine how cells ensure the accurate translation of the genetic code, and how changes in the underlying processes impact cellular health and contribute to microbial pathogenesis and disease. Many of these processes are essential and unique to particular systems, making them ideal potential drug targets.
Quality control in protein synthesis
Ribosomes are the protein synthesis factories of the cell that translate the codons of mRNA into amino acids. Protein synthesis proceeds by delivery to the ribosome of aminoacyl-tRNAs, which pair with the corresponding mRNA sequences. Aminoacyl-tRNAs are made by the aminoacyl-tRNA synthetases, a family of twenty proteins each of which pairs a particular amino acid with the correct tRNA. Accurate aminoacyl-tRNA synthesis often requires an additional editing activity intrinsic to many aaRSs. The editing activity significantly decreases the level of mistakes in aminoacyl-tRNA synthesis in vitro and in vivo, although quantitative analysis of its contribution to the overall fidelity of translation has not been performed. The overall aim of our work is to develop experimental systems to quantitatively measure the frequency of aaRS-dependent misincorporation for several amino acids and evaluate the contribution of aaRS editing to overall translational fidelity in vivo.
Translational control of antibiotic resistance
In responses to different environmental stresses, such as the presence of antibiotics, microbes direct resources away from translation to a variety of pathways that contribute to resistance. Elongation factor P (EF-P). EF-P is a protein that mimics the structure and function of a tRNA and binds ribosomes. Aminoacylatio
n of EF-P is required for optimal growth under a variety of conditions, for example at key points during Salmonella infection. We are interested in understanding how EF-P mimics tRNA at the molecular level and how this provides a novel mechanism for the post-transcriptional control of gene expression.
FIGURE 1: The role of EF-P in M. aeruginosavorus during host invasion. The far left panel depicts P. aeruginosa drawn in purple and M. aeruginosavorus in yellow.
(A) The image illustrates a breach in the outer membrane allowing for dTDP-L-rhamnose to diffuse into M. aeruginosavorus where EF-P (red) is then modified by EarP (white).
(B) As a result of EF-P being modified ribosomes (grey and purple) can effectively translate mRNA (blue) with a poly-proline stretch.
(C) On the other hand during the attack phase EF-P is unmodified and therefore poly-proline translation is absent.
(Rajkovic et al. 2015)