Adenylylsulfate reductases from archaea and bacteria are 1:1 αβ-heterodimeric iron-sulfur flavoenzymes -: high similarity of molecular properties emphasizes their central role in sulfur metabolism

Highly active adenylylsulfate (APS) reductase was isolated under N-2/H-2 from sulfate-reducing and sulfide-oxidizing bacteria and archaea, It tvas a I:I alpha beta-heterodimer of molecular mass approximate to 95 kDa, and two subunits (alpha approximate to 75, beta approximate to 20 kDa), The specific activity was 11-14 mu mol (min mg)(-1); cofactor analysis revealed 0.96 +/- 0.05 FAD, 7.5 +/- 0.1 Fe and 7.9 +/- 0.25 S2-. The photochemically reduced enzyme had a multiline EPR spectrum resulting from two interacting [4Fe-4S] centers. The properties of the different APS reductases were remarkably similar, although the enzyme is involved in different metabolic pathways and was isolated from phylogenetically far separated organisms. A structural model is proposed, with FAD bound to the alpha-subunit, and two [4FE-4S] centers located in close proximity on the beta-subunit. (C) 2000 Federation of European Biochemical Societies.