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Int. J. Mol. Sci. 2014, 15(2), 3204-3219;

A New Pepstatin-Insensitive Thermopsin-Like Protease Overproduced in Peptide-Rich Cultures of Sulfolobus solfataricus

Institute of Biosciences and BioResources, National Research Council (CNR-IBBR), Via Pietro Castellino 111, Naples 80131, Italy
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Received: 5 December 2013 / Revised: 26 January 2014 / Accepted: 11 February 2014 / Published: 21 February 2014
(This article belongs to the Special Issue Thermophilic DNases, RNases and Proteases)
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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. View Full-Text
Keywords: Sulfolobus solfataricus; thermopsin; thermophilic enzyme; signal-transduction pathways Sulfolobus solfataricus; thermopsin; thermophilic enzyme; signal-transduction pathways
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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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.

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