InterPro domain: IPR015939

This entry represents a domain with a spectrin-repeat-like fold consisting of three helices in a closed bundle with a left-handed twist. This domain is found in the succinate dehydrogenase/fumarate reductase oxidoreductase family of proteins, such as:

• L-aspartate oxidase ( 1.4.3.16 ), a flavoenzyme component of the bacterial quinolinate synthase system that catalyses the conversion of L-aspartate to oxaloacetate, the first step in the de novo biosynthesis of NAD+ [ 1 , 2 ].

• Fumarate reductase, which is part of the quinol-fumarate reductase (QFR) respiratory complex that catalyses the terminal step of anaerobic respiration when fumarate acts as the terminal electron acceptor [ 3 ].

• Succinate dehydrogenase (SQR; 1.3.5.1 ), an iron-sulphur flavoenzyme from bacteria that is analogous to the mitochondrial respiratory complex II, forming part of the electron transport pathway from the electron acceptor (succinate) to the terminal donor (ubiquinone) [ 4 ].

• Adenylylsulphate reductase A subunit ( 1.8.4 ), an iron-sulphur flavoenzyme that catalyses the reversible reduction of adenosine-5'-phosphate (APS) to sulphite and AMP [ 5 ].

1. Structure of FAD-bound L-aspartate oxidase: insight into substrate specificity and catalysis. Biochemistry 41, 3018-24
2. Structure of L-aspartate oxidase: implications for the succinate dehydrogenase/fumarate reductase oxidoreductase family. Structure 7, 745-56
3. Crystallographic studies of the Escherichia coli quinol-fumarate reductase with inhibitors bound to the quinol-binding site. J. Biol. Chem. 277, 16124-30
4. Architecture of succinate dehydrogenase and reactive oxygen species generation. Science 299, 700-4
5. Structure of adenylylsulfate reductase from the hyperthermophilic Archaeoglobus fulgidus at 1.6-A resolution. Proc. Natl. Acad. Sci. U.S.A. 99, 1836-41