Ligands to the 2Fe iron‐sulfur center in succinate dehydrogenase

Abstract
Membrane‐bound succinate oxidoreductases are flavoenzymes containing one each of a 2Fe, a 3Fe and a 4Fe iron‐sulfur center. Amino acid sequence homologies indicate that all three centers are located in the Ip (B) subunit. From polypeptide and gene analysis of Bacillus subtillis succinate dehydrogenase‐defective mutants combined with earlier EPR spectroscopic data, we show that four conserved cysteine residues in the first half of Ip are the ligands to the [2Fe‐2S] center. These four residues have previously been predicted to be the ligands. Our results also suggest that the N‐terminal part of B. subtilis Ip constitutes a domain which can incorporate separately the 2Fe center and interact with Fp, the flavin‐containing subunit of the dehydrogenase.