In every living organism, proteins are faithfully synthesized with high fidelity. A family of enzymes, called the aminoacyl-tRNA synthetases, is responsible for the first step of protein synthesis. In this step specific amino acids are attached to their cognate tRNAs. Some of these enzymes are prone to mistakes (attaching the wrong amino acid to the tRNA) and as a consequence, have developed proofreading and editing mechanisms to reduce mistakes and ensure high fidelity. A high level of accuracy is critical to the proper functioning and viability of each cell. This project will investigate unusual examples of the aminoacyl-tRNA synthetases, which appear to have compromised proofreading and editing mechanisms. One case exists in an ancient archae called Sulfolobus that thrives at high temperatures under acidic conditions typical of hot springs. A different paradigm exists in Mycoplasma, an organism that has undergone genome reduction. This reduced genome has selectively sacrificed the fidelity modules in one of these synthetase enzymes. It is possible that the fidelity mechanisms in these organisms have been compromised in order to provide an innovative pathway to confer a selective advantage. Alternatively, these enzymes might have adapted to rely on novel fidelity mechanisms. The goals of this project have potential to shift existing paradigms about the evolution and fidelity of protein synthesis as well as the maintenance of the genetic code. The project may uncover novel biological mechanisms for cell adaptation and natural selection.
Broader Impacts: This project is committed to enhancing scientific literacy of the public via outreach efforts to young children in pre-school and elementary school classrooms. An academic module with an experimental component will introduce students to microbiology and the three kingdoms of life. This module is designed to educate young children in fundamental biology concepts and is expected to broadly impact and stimulate their interest in science. Graduate student training and mentoring will be integrated throughout the research and education plan to enhance professional and scientific development as well as to provide role models to young children as well as undergraduate researchers.
Mycoplasma organisms were discovered to have evolved a systematic loss of functions that resulted in a decrease in fidelity for the synthesis of proteins. This loss was centered on an essential family of proteins, called the tRNA synthetases, which sets the genetic code by linking specific amino acids via an RNA adaptor molecule. Mistakes by these tRNA synthetase enzymes can be self-corrected by editing mechanisms. In Mycoplasma, some of these editing mechanisms have been ablated resulting in infidelities. It is hypothesized that this is to establish a persistent relationship with a host species that these organisms are dependent. This works showed that the tRNA synthetases have been fine-tuned to dial up or down fidelity of protein synthesis by the addition of protein modules that not only confer a mechanism for editing, but also dictate specificity of the substrate in a distance reaction site. This project also included outreach to young children to stimulate their interest in the biological and chemical sciences, as well as provided role model scientists. Pre-school and young elementary school children were introduced to the world of bacteria and also chemistry via hands-on experimental approaches and descriptions that described these processes. The children "hunted" for bacteria in their classroom environments by swabbing areas and growing these "invisible" organisms on rich nutrients. They visited the laboratory at the University to see scientists at the bench and do chemistry and microbiology experiments. Graduate students, Postdoctoral Associates, and Professors were involved in this outreach project and also served as valuable role models for these young children.
