Archaeal Sec-Dependent Protein Translocation

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All cells need to translocate proteins into and across hydrophobic membranes to interact with their environment. Most proteins are translocated in an unfolded conformation by the Sec pathway via a universally conserved proteinaceous pore. A number of non-conserved accessory components, which are distinct in bacteria and eukaryotes, are also necessary for efficient transport via this pathway. Surprisingly, the archaeal Sec machinery contains a combination of homologs of bacterial and eukaryotic Sec components, which raises questions regarding the mechanism of translocation in archaea. In addition, in bacteria and yeast, distinct translocation ATPases are required to provide energy for protein transport, yet no archaeal homolog of either of these ATPases has been identified. Thus, the energetics driving the net unidirectional movement of proteins through the archaeal Sec pore remains unknown. The goal of this project is to isolate and characterize archaeal Sec translocation mutants in the model haloarchaeon Haloferax volcanii using two complementary genetic selection strategies. Importantly, these selections have the potential to identify novel Sec components, including components that are unique to archaea (such as a novel translocation ATPase) as well as components that have bacterial and/or eukaryotic homologs, which were not previously known to participate in Sec translocation. Together, this research is likely to further the knowledge of the Sec translocation pathway in all domains of life. Moreover, a better understanding of archaea, which often inhabit "extreme" environments, will allow the investigator to define the boundaries of biological processes in the biosphere, and has the potential to reveal information about the origin and evolution of the three domains of life. This project is fostering the training of students at all levels. Undergraduate students interested in education are doing out reach as part of a university course to intercity schools to demonstrate basic principles of microbial research.