Structural Analysis of a Nitrogenase Iron Protein from Methanosarcina acetivorans: Implications for CO2 Capture by a Surface-Exposed [Fe4S4] Cluster
- Authors
- Rettberg, Lee A.; Kang, Wonchull; Stiebritz, Martin T.; Hiller, Caleb J.; Lee, Chi Chung; Liedtke, Jasper; Ribbe, Markus W.; Hu, Yilin
- Issue Date
- Jul-2019
- Publisher
- American Society for Microbiology
- Keywords
- CO2 capture; FeS cluster; iron protein; methanogen; nitrogenase
- Citation
- mBio, v.10, no.4
- Journal Title
- mBio
- Volume
- 10
- Number
- 4
- URI
- http://scholarworks.bwise.kr/ssu/handle/2018.sw.ssu/40944
- DOI
- 10.1128/mBio.01497-19
- ISSN
- 2150-7511
- Abstract
- Nitrogenase iron (Fe) proteins reduce CO2 to CO and/or hydrocarbons under ambient conditions. Here, we report a 2.4-angstrom crystal structure of the Fe protein from Methanosarcina acetivorans (MaNifH), which is generated in the presence of a reductant, dithionite, and an alternative CO2 source, bicarbonate. Structural analysis of this methanogen Fe protein species suggests that CO2 is possibly captured in an unactivated, linear conformation near the [Fe4S4] cluster of MaNifH by a conserved arginine (Arg) pair in a concerted and, possibly, asymmetric manner. Density functional theory calculations and mutational analyses provide further support for the capture of CO2 on MaNifH while suggesting a possible role of Arg in the initial coordination of CO2 via hydrogen bonding and electrostatic interactions. These results provide a useful framework for further mechanistic investigations of CO2 activation by a surface-exposed [Fe4S4] cluster, which may facilitate future development of FeS catalysts for ambient conversion of CO2 into valuable chemical commodities. IMPORTANCE This work reports the crystal structure of a previously uncharacterized Fe protein from a methanogenic organism, which provides important insights into the structural properties of the less-characterized, yet highly interesting archaeal nitrogenase enzymes. Moreover, the structure-derived implications for CO2 capture by a surface-exposed [Fe4S4] cluster point to the possibility of developing novel strategies for CO2 sequestration while providing the initial insights into the unique mechanism of FeS-based CO2 activation.
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