Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10536796 | Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics | 2015 | 8 Pages |
Abstract
5â²-Deoxy-5â²-methylthioadenosine phosphorylase from Sulfolobus solfataricus is a hexameric hyperthermophilic protein containing in each subunit two pairs of disulfide bridges, a CXC motif, and one free cysteine. The contribution of each disulfide bridge to the protein conformational stability and flexibility has been assessed by comparing the thermal unfolding and the limited proteolysis of the wild-type enzyme and its variants obtained by site-directed mutagenesis of the seven cysteine residues. All variants catalyzed efficiently MTA cleavage with specific activity similar to the wild-type enzyme. The elimination of all cysteine residues caused a substantial decrease of ÎHcal (850 kcal/mol) and Tmax (39 °C) with respect to the wild-type indicating that all cysteine pairs and especially the CXC motif significantly contribute to the enzyme thermal stability. Disulfide bond Cys200-Cys262 and the CXC motif weakly affected protein flexibility while the elimination of the disulfide bond Cys138-Cys205 lead to an increased protease susceptibility. Experimental evidence from limited proteolysis, differential scanning calorimetry, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing and nonreducing conditions also allowed to propose a stabilizing role for the free Cys164.
Keywords
MTAHyperthermophilic enzymes5′-deoxy-5′-methylthioadenosine[θ]NDSBMOPSPDIPNPAdoMetGdmCl3-(N-morpholino) propanesulfonic acidS-adenosylmethioninesodium dodecyl sulfate-polyacrylamide gel electrophoresisSDS-PAGEcircular dichroismProtein thermostabilityLimited proteolysisDisulfide bridgesPurine nucleoside phosphorylaseDifferential scanning calorimetryguanidinium chloride
Related Topics
Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
Maria Libera Bagarolo, Marina Porcelli, Elisa Martino, Georges Feller, Giovanna Cacciapuoti,