A new protease, named SsMTP was identified from the archeon Sulfolobus solfataricus. The enzyme is associated to the cell-membrane and over-produced in response to the peptide-enriched media. SsMTP has a molecular mass of 120 kDa showing optimal activity at pH 2.0 in the temperature range 70 - 90 degrees C, and a half-life of 20 days at 80 degrees C. Primary structure analysis revealed that SsMTP represents a novel type of multi-domain thermopsin-like protease containing the catalytic domain followed by two distinct domains, PKD and Y_Y_Y, which are usually involved in a range of protein-protein interactions among the extracellular proteins.