Microbiology & Virology

An Orphan Protein Drove The Ecological Expansion Of Nitrogen Fixation

By Keith Cowing
Status Report
April 10, 2023
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An Orphan Protein Drove The Ecological Expansion Of Nitrogen Fixation
Structure and genetics of the nitrogenase G-subunit. A) Left, crystallographic structure of the extant A. vinelandii Vnf nitrogenase complex (VnfH, PDB 6Q9336; VnfDGK, PDB 5N6Y22 ) containing the G-subunit (dark blue). The Anf nitrogenase is inferred to be comparable in its multimeric structure, binding FeFe-co instead of FeV-co. Right, crystallographic structure of the extant Nif nitrogenase complex (NifH, PDB 1M3437; NifDK, PDB 3U7Q38) lacking the G subunit. B) Secondary structure of the Vnf G-subunit. C) Arrangement of the Nif, Vnf, and Anf structural genes in A. vinelandii. Vnf/AnfG (dark blue) is located between Vnf/AnfD and Vnf/AnfK genes. — biorxiv.org

Nitrogenases have catalyzed biological nitrogen fixation for billions of years and revolutionized planet Earth by supplying essential nitrogen to the biosphere.

How these molecular machines were built and distributed by microbial processes and a shifting geochemical landscape remains an open question.

Here, we probe the birth and functional evolution of the G-subunit, an integral, Precambrian component of certain nitrogenases that makes its appearance midway through the history of nitrogen fixation. Our results establish the G-subunit as an unprecedented molecular novelty that was integrated into preexisting interaction pathways for nitrogenase metallocluster incorporation.

In the wake of Earth oxygenation, the G-subunit primed nitrogenases and their microbial hosts to exploit newly diversified geochemical environments. The history of the nitrogenase G-subunit showcases the elaborate tango between contingent evolutionary events and environmental conditions that together open an adaptive frontier for molecular innovations with global consequences.

Bruno Cuevas Zuviria, Amanda K. Garcia, Brooke Carruthers, Betul Kacar



Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) πŸ––πŸ»