DISSIMILATORY ATP SULFURYLASE FROM THE HYPERTHERMOPHILIC SULFATE REDUCER ARCHAEOGLOBUS-FULGIDUS BELONGS TO THE GROUP OF HOMOOLIGOMERIC ATP SULFURYLASES

In the hyperthermophilic sulfate reducer Archaeoglobus fulgidus DSM 43 04(T), two open reading frames (sat and ORF2) are located upstream of the aprBA genes encoding adenosine-5'-phosphosulfate (APS) reductase. sat-ORF2-aprBA probably form a transcriptional unit, since sat is prec eded by putative promoter sequences and termination signals are found downstream of aprA. While the 117-residue ORF2 product does not show s ignificant similarity to known proteins, the 456-residue, 52.78-kDa. s at-encoded polypeptide exhibits similarity to the homo-oligomeric aden osine triphosphate (ATP) sulfurylases from sulfur-oxidizing bacteria a nd from sulfate-assimilating bacteria and eukaryotes. Functional overe xpression of sat in Escherichia coli proved that the encoded protein a cts as an ATP sulfurylase. The recombinant protein was purified to hom ogeneity and found to be a homo-dimer. Comparison of sulfate and thios ulfate grown A. fulgidus revealed that ATP sulfurylase and APS reducta se are constitutive enzymes. Distance matrix analyses allowed insights into the evolution of prokaryotic ATP sulfurylases. (C) 1998 Publishe d by Elsevier Science B.V.