- The presence of an iron-sulfur cluster in adenosine 5'-phosphosulfate reductase separates organisms utilizing adenosine 5'-phosphosulfate and phosphoadenosine 5'-phosphosulfate for sulfate assimilation. Kopriva, S., Büchert, T., Fritz, G., Suter, M., Benda, R., Schünemann, V., Koprivova, A., Schürmann, P., Trautwein, A.X., Kroneck, P.M., Brunold, C. J. Biol. Chem. (2002)