Cryo-EM reveals a composite flavobicluster electron bifurcation site in the Bfu family member NfnABC.

ABSTRACT: The BfuABC family is a diverse group of electron bifurcating enzymes that play key roles in anaerobic microbial metabolism. Previous studies have focused almost exclusively on the BfuABC-type hydrogenases but the mechanism and site of electron bifurcation remain unknown. Herein we focus on the Caldicellulosiruptor saccharolyticus (Csac) NfnABC-type Bfu enzyme that catalyzes the oxidation of NADPH and simultaneous reduction of NAD and the redox protein ferredoxin (Fd). Cryo-EM structures determined with and without NAD and Fd reveal seven FeS clusters and one FAD in NfnA, one FeS cluster in NfnC, and three FeS clusters, two Zn ions, and one FMN in NfnB. The Zn ions take the place of FeS clusters previously proposed in other Bfu family members. Csac Nfn for the first time defines the minimum

SUBMITTER: Li H 

PROVIDER: S-EPMC11829005 | biostudies-literature | 2025 Feb

REPOSITORIES: biostudies-literature