Structural highlights
FunctionPublication Abstract from PubMedElectron bifurcation enables thermodynamically unfavorable biochemical reactions. Four groups of bifurcating flavoenzyme are known and three use FAD to bifurcate. FeFe-HydABC hydrogenase represents the fourth group, but its bifurcation site is unknown. We report cryo-EM structures of the related NiFe-HydABCSL hydrogenase that reversibly oxidizes H(2) and couples endergonic reduction of ferredoxin with exergonic reduction of NAD. FMN surrounded by a unique arrangement of iron sulfur clusters forms the bifurcating center. NAD binds to FMN in HydB, and electrons from H(2) via HydA to a HydB [4Fe-4S] cluster enable the FMN to reduce NAD. Low-potential electron transfer from FMN to the HydC [2Fe-2S] cluster and subsequent reduction of a uniquely penta-coordinated HydB [2Fe-2S] cluster require conformational changes, leading to ferredoxin binding and reduction by a [4Fe-4S] cluster in HydB. This work clarifies the electron transfer pathways for a large group of hydrogenases underlying many essential functions in anaerobic microorganisms. Structure and electron transfer pathways of an electron-bifurcating NiFe-hydrogenase.,Feng X, Schut GJ, Haja DK, Adams MWW, Li H Sci Adv. 2022 Feb 25;8(8):eabm7546. doi: 10.1126/sciadv.abm7546. Epub 2022 Feb , 25. PMID:35213221[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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