Archaea (formerly archaebacteria) comprise a domain of life that is phylogenetically distinct from both Eucarya and Bacteria. Here we report the cloning of a gene from the Archaeon Sulfolobus shibatae that encodes a protein with strong homology to the TATA binding protein (TBP) of eukaryotes. Sulfolobus shibatae TBP is, however, almost as diverged from other archaeal TBPs that have been cloned as it is from eukaryotic TBPs. DNA binding studies indicate that S.shibatae TBP recognizes TATA-like A-box sequences that are present upstream of most archaeal genes. By quantitatively immunodepleting S.shibatae TBP from an in vitro transcription system, we demonstrate that Sulfolobus RNA polymerase is capable of transcribing the 16S/23S rRNA promoter weakly in the absence of TBP. Most significantly, we show that addition of recombinant S.shibatae TBP to this immunodepleted system leads to transcriptional stimulation and that this stimulation is dependent on the A-box sequence of the promoter. Taken together, these findings reveal fundamental similarities between the transcription machineries of Archaea and eukaryotes.