1. Multiple disulfide bridges modulate conformational stability and flexibility in hyperthermophilic archaeal purine nucleoside phosphorylase.
- Author
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Bagarolo ML, Porcelli M, Martino E, Feller G, and Cacciapuoti G
- Subjects
- Adenosine chemistry, Adenosine metabolism, Amino Acid Motifs, Archaeal Proteins genetics, Archaeal Proteins metabolism, Enzyme Stability, Escherichia coli genetics, Escherichia coli metabolism, Gene Expression, Hot Temperature, Kinetics, Molecular Sequence Data, Mutagenesis, Site-Directed, Mutation, Protein Conformation, Purine-Nucleoside Phosphorylase genetics, Purine-Nucleoside Phosphorylase metabolism, Recombinant Proteins chemistry, Recombinant Proteins genetics, Recombinant Proteins metabolism, Substrate Specificity, Sulfolobus solfataricus enzymology, Thermodynamics, Thionucleosides metabolism, Adenosine analogs & derivatives, Archaeal Proteins chemistry, Cysteine chemistry, Disulfides chemistry, Purine-Nucleoside Phosphorylase chemistry, Sulfolobus solfataricus chemistry, Thionucleosides chemistry
- Abstract
5'-Deoxy-5'-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 ΔHcal (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., (Copyright © 2015 Elsevier B.V. All rights reserved.)
- Published
- 2015
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