Unraveling nickel delivery pathways in methanogenic archaea

Metal ions are essential for the proper structures and functions of many proteins. The efficient incorporation of correct metals into respective client proteins is critical for life; however, high levels of free metals are toxic to cells. Thus, many metal-dependent proteins require helper proteins – termed metallochaperones – that sequester and deliver specific metals to the correct client proteins. This project is focused on metallochaperones involved in nickel delivery pathways in methanogenic archaea (methanogens), which are microorganisms that produce methane as a by-product of their unique energy metabolism know as methanogenesis. Methanogens are uniquely dependent on nickel as a micronutrient since they employ several different nickel-dependent enzymes. However, the putative nickel metallochaperones remain poorly defined. Thus, this project will elucidate the proteins involved in trafficking and delivering nickel to each of the different nickel-dependent enzymes in these organisms. The knowledge gained from this project could support efforts to engineer methanogenic metabolism to produce biofuels and commodity chemicals from low-cost precursors. In addition to providing training and professional development opportunities to undergraduate and graduate students, the project will engage middle- and high-school students in hands-on microbiology activities to highlight the key role of microbes in diverse natural environments and in biotechnology. Methanogens have several different nickel-dependent enzymes that play key roles at the interface of energy metabolism and carbon assimilation. However, minimal knowledge exists regarding nickel homeostasis – including nickel uptake, nickel storage/export, and nickel-dependent enzyme assembly – in these organisms. Thus, this project will employ in vivo crosslinking, quantitative proteomics, targeted gene deletions, and in vitro biochemical experiments to define the nickel delivery networks and elucidate the functions and physiological significance of a series of nickel metallochaperones that are responsible for delivering nickel to each of the respective nickel-dependent enzymes. Model methanogens with highly developed genetic tools are emerging as biotechnologically useful hosts to produce valuable molecules from low-cost precursors. Thus, the knowledge gained in this project could be employed to modulate the activities of nickel-dependent enzymes in methanogens to direct metabolism toward the production of desired molecules. This project is supported by the Systems and Synthetic Biology Cluster in the Molecular and Cellular Biosciences Division of the Directorate for Biological Sciences. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.