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.
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Gogliettino, M.; Riccio, A.; Cocca, E.; Rossi, M.; Palmieri, G.; Balestrieri, M. A New Pepstatin-Insensitive Thermopsin-Like Protease Overproduced in Peptide-Rich Cultures of Sulfolobus solfataricus. Int. J. Mol. Sci. 2014, 15, 3204-3219.
Gogliettino M, Riccio A, Cocca E, Rossi M, Palmieri G, Balestrieri M. A New Pepstatin-Insensitive Thermopsin-Like Protease Overproduced in Peptide-Rich Cultures of Sulfolobus solfataricus. International Journal of Molecular Sciences. 2014; 15(2):3204-3219.
Gogliettino, Marta; Riccio, Alessia; Cocca, Ennio; Rossi, Mosè; Palmieri, Gianna; Balestrieri, Marco. 2014. "A New Pepstatin-Insensitive Thermopsin-Like Protease Overproduced in Peptide-Rich Cultures of Sulfolobus solfataricus." Int. J. Mol. Sci. 15, no. 2: 3204-3219.