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Nitrogenase M-Cluster Assembly: Tracing the ‘9th Sulfur’ of the Nitrogenase Cofactor via a Semi-Synthetic Approach

Prof. Markus W. Ribbe
Prof. Markus W. Ribbe
University of California at Irvine
Chemistry Building, Room 400
Inorganic Seminar
CMS Seminar

The M-cluster is the active site of nitrogenase that contains an 8Fe-core assembled via coupling and rearrangement of two [Fe4S4] clusters concomitant with the insertion of an interstitial carbon and a ‘9th sulfur’. Combining synthetic [Fe4S4] clusters with an assembly protein template, we show that sulfite gives rise to the ‘9th sulfur’ that is incorporated in the catalytically important belt region of the cofactor after the radical SAM-dependent carbide insertion and the concurrent 8Fe-core rearrangement have already taken place. This work provides a semi-synthetic tool for strategically labeling the cofactor—including its ‘9th S’ in the belt region—for mechanistic investigations of nitrogenase while suggesting an interesting link between nitrogen fixation and sulfite detoxification in diazotrophic organisms.


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