A GENE FROM THE HYPERTHERMOPHILE PYROCOCCUS-FURIOSUS WHOSE DEDUCED PRODUCT IS HOMOLOGOUS TO MEMBERS OF THE PROLYL OLIGOPEPTIDASE FAMILY OF PROTEASES

The mlr-2 gene from the hyperthermophilic archaeum Pyrococcus furiosus was identified from a family of clones whose expression was influenced by the presence of maltose in the medium. The sequence of 2100 bp of DNA containing mlr-2 and its flanking regions revealed a 616-amino-acid (71 kDa) open reading frame (ORF). The ORF's initiation codon appeared 10 nt into the mlr-2 message and was not preceded by any apparent ribosome-binding site. The deduced product shared homology with prolyl endopeptidases from both eukaryotic and eubacterial sources (52-57% similarity, 30-37% identity) and signature domains containing the Ser-Asp-His triad, which is characteristic of this family of proteases, were present. Northern blot experiments revealed the presence of an approx. 2.0-kb transcript in P. furiosus extracts, corresponding in length to that expected from mlr-2 expression. Initiation of transcription occurred 23 bp downstream from a putative BoxA promoter element.