title: A new pepstatin-insensitive thermopsin-like protease overproduced in peptide-rich cultures of Sulfolobus solfataricus.
abstract: In this study, we gain insight into the extracellular proteolytic system of Sulfolobus solfataricus grown on proteinaceous substrates, providing further evidence that acidic proteases were specifically produced in response to peptide-rich media. The main proteolytic component was the previously isolated SsMTP (Sulfolobus solfataricus multi-domain thermopsin-like protease), while the less abundant (named SsMTP-1) one was purified, characterized and identified as the sso1175 gene-product. The protein revealed a multi-domain organization shared with the cognate SsMTP with a catalytic domain followed by several tandemly-repeated motifs. Moreover, both enzymes were found spread across the Crenarchaeota phylum and belonging to the thermopsin family, although segregated into diverse phylogenetic clusters. SsMTP-1 showed a 75-kDa molecular mass and was stable in the temperature range 50-90 °C, with optimal activity at 70 °C and pH 2.0. Serine, metallo and aspartic protease inhibitors did not affect the enzyme activity, designating SsMTP-1 as a new member of the pepstatin-insensitive aspartic protease family. The peptide-bond-specificity of SsMTP-1 in the cleavage of the oxidized insulin B chain was uncommon amongst thermopsins, suggesting that it could play a distinct, but cooperative role in the protein degradation machinery. Interestingly, predictions of the transmembrane protein topology of SsMTP and SsMTP-1 strongly suggest a possible contribution in signal-transduction pathways.
authors.affiliation: Institute of Biosciences and BioResources, National Research Council (CNR-IBBR), Via Pietro Castellino 111, Naples 80131, Italy. marta.gogliettino@ibbr.cnr.it.
authors.forename: Marta
authors.initials: M
authors.lastname: Gogliettino
authors.affiliation: Institute of Biosciences and BioResources, National Research Council (CNR-IBBR), Via Pietro Castellino 111, Naples 80131, Italy. alessia.riccio@ibbr.cnr.it.
authors.forename: Alessia
authors.initials: A
authors.lastname: Riccio
authors.affiliation: Institute of Biosciences and BioResources, National Research Council (CNR-IBBR), Via Pietro Castellino 111, Naples 80131, Italy. ennio.cocca@ibbr.cnr.it.
authors.forename: Ennio
authors.initials: E
authors.lastname: Cocca
authors.affiliation: Institute of Biosciences and BioResources, National Research Council (CNR-IBBR), Via Pietro Castellino 111, Naples 80131, Italy. m.rossi@ibp.cnr.it.
authors.forename: Mosè
authors.initials: M
authors.lastname: Rossi
authors.affiliation: Institute of Biosciences and BioResources, National Research Council (CNR-IBBR), Via Pietro Castellino 111, Naples 80131, Italy. gianna.palmieri@ibbr.cnr.it.
authors.forename: Gianna
authors.initials: G
authors.lastname: Palmieri
authors.affiliation: Institute of Biosciences and BioResources, National Research Council (CNR-IBBR), Via Pietro Castellino 111, Naples 80131, Italy. marco.balestrieri@ibbr.cnr.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Balestrieri
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D003470:Culture Media / Q000494:pharmacology; D010450:Endopeptidases / Q000737:chemistry / Q000378:metabolism; D018093:Gelatinases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D010436:Pepstatins / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry*; D010802:Phylogeny; D013379:Substrate Specificity; D048229:Sulfolobus solfataricus / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D013696:Temperature
chemical_list: D019843:Archaeal Proteins; D003470:Culture Media; D010436:Pepstatins; D010455:Peptides; D010450:Endopeptidases; D010447:Peptide Hydrolases; C062465:thermopsin; D018093:Gelatinases; C031375:pepstatin