RUI: Evolution of Bacterial Asparaginyl-tRNA Synthesis

Skidmore College, Saratoga Springs NY

Investigators

Abstract

The goal of this research is to understand why certain bacteria employ two distinct routes for preparing the amino acid asparagine for protein synthesis. The results will provide insights into the evolutionary origin of these alternate pathways and how they may confer adaptive physiological advantages to bacteria growing in different natural environments, i.e., in soil versus inside a mammalian host. Undergraduate students, including members of underrepresented minorities, will be trained in laboratory research through the project. The impact of the training will be measured by the presentation of the research at scientific meetings, student co-authorship of peer reviewed articles, and future student placement in the workforce and in graduate programs. In addition, the project will allow studies arising from the research to be integrated into an experimental biochemistry laboratory course, training additional undergraduate students in hypothesis driven biochemical research. To expand scientific literacy and retain more students from underrepresented minorities in STEM disciplines, the project will provide outreach to middle school students. Translation of a genetic message into the amino acid sequence of a protein is essential for cellular life. The fidelity of the process is dependent on the formation of the correct adaptor molecules, aminoacyl-tRNAs. Attaching an amino acid to the right tRNA is carried out in cells primarily by aminoacyl-tRNA synthetases. Each tRNA synthetase is specific for one amino acid and only ligates the amino acid onto a certain set of tRNA molecules. However, in many bacterial genomes asparaginyl-tRNA synthetase that directly attaches asparagine to its cognate tRNA is not encoded. Instead these organisms synthesize asparagine on the tRNA via an indirect two-step pathway. First they use a non-discriminating aspartyl-tRNA synthetase to aminoacylate tRNA with aspartate. The tRNA-bound Asp is then amidated by the amidotransferase GatCAB to form asparaginyl-tRNA. A number of bacteria, including Bacillus subtilis and Bacillus halodurans, encode both routes for asparaginyl-tRNA synthesis. A subset of bacteria encoding both routes acquired an archaeal non-discriminating aspartyl-tRNA synthetase for tRNA-dependent asparagine biosynthesis. The objectives of this project are to use biochemical and microbial genetic approaches to elucidate why so many bacteria retain both routes for asparaginyl-tRNA formation and why certain bacteria acquired an archaeal non-discriminating aspartyl-tRNA synthetase for the task. Results are expected to shed light on the evolution of a process that is crucial for the accuracy of protein synthesis.