Nitrogenase resurrection and the evolution of a singular enzymatic mechanism
- University of Wisconsin-Madison, United States
- Utah State University, United States
Abstract
The planetary biosphere is powered by a suite of key metabolic innovations that emerged early in the history of life. However, it is unknown whether life has always followed the same set of strategies for performing these critical tasks. Today, microbes access atmospheric sources of bioessential nitrogen through the activities of just one family of enzymes, nitrogenases. Here, we show that the only dinitrogen reduction mechanism known to date is an ancient feature conserved from nitrogenase ancestors. We designed a paleomolecular engineering approach wherein ancestral nitrogenase genes were phylogenetically reconstructed and inserted into the genome of the diazotrophic bacterial model, Azotobacter vinelandii, enabling an integrated assessment of both in vivo functionality and purified nitrogenase biochemistry. Nitrogenase ancestors are active and robust to variable incorporation of one or more ancestral protein subunits. Further, we find that all ancestors exhibit the reversible enzymatic mechanism for dinitrogen reduction, specifically evidenced by hydrogen inhibition, that is also exhibited by extant A. vinelandii nitrogenase isozymes. Our results suggest that life may have been constrained in its sampling of protein sequence space to catalyze one of the most energetically challenging biochemical reactions in nature. The experimental framework established here is essential for probing how nitrogenase functionality has been shaped within a dynamic, cellular context to sustain a globally consequential metabolism.
Data availability
MATERIALS AVAILABILITYMaterials including bacterial strains and plasmids are available to the scientific community upon request.DATA AND CODE AVAILABILITYPhylogenetic data, including sequence alignments and phylogenetic trees, and the script for ancestral gene codon-optimization are publicly available at https://github.com/kacarlab/garcia_nif2023. All other data are included as source data and supplementary files.
Article and author information
Author details
Funding
National Aeronautics and Space Administration (19- ICAR19_2-0007)
- Amanda K Garcia
- Derek F Harris
- Alex J Rivier
- Brooke M Carruthers
- Azul Pinochet-Barros
- Lance Seefeldt
- Betül Kaçar
National Aeronautics and Space Administration (Postdoctoral Fellowship)
- Amanda K Garcia
University of Wisconsin-Madison
- Betül Kaçar
Arizona Space Grant Consortium
- Brooke M Carruthers
National Aeronautics and Space Administration (80NSSC19K1617)
- Betül Kaçar
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2023, Garcia et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Nitrogenase resurrection and the evolution of a singular enzymatic mechanism
eLife 12:e85003.
https://doi.org/10.7554/eLife.85003
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