title: Biochemical characterization and homology modeling of a purine-specific ribonucleoside hydrolase from the archaeon Sulfolobus solfataricus: insights into mechanisms of protein stabilization.
abstract: We report the biochemical and structural characterization of the purine-specific ribonucleoside hydrolase from the archaeon Sulfolobus solfataricus (SsIAG-NH). SsIAG-NH is a homodimer of 70kDa specific for adenosine, guanosine and inosine. SsIAG-NH is highly thermophilic and is characterized by extreme thermodynamic stability (T(m), 107 degrees C), kinetic stability and remarkable resistance to guanidinium chloride-induced unfolding. A disulfide bond that, on the basis of SDS-PAGE is positioned intersubunits, plays an important role in thermal stability. SsIAG-NH shares 43% sequence identity with the homologous pyrimidine-specific nucleoside hydrolase from S. solfataricus (SsCU-NH). The comparative sequence alignment of SsIAG-NH, SsCU-NH, purine non-specific nucleoside hydrolase from Crithidia fasciculata and purine-specific nucleoside hydrolase from Trypanosoma vivax shows that, only few changes in the base pocket are responsible for different substrate specificity of two S. solfataricus enzymes. The structure of SsIAG-NH predicted by homology modeling allows us to infer the role of specific residues in substrate specificity and thermostability.
authors.affiliation: Dipartimento di Biochimica e Biofisica "F. Cedrangolo", Seconda Università di Napoli, Italy. marina.porcelli@unina2.it
authors.forename: Marina
authors.initials: M
authors.lastname: Porcelli
authors.forename: Iolanda
authors.initials: I
authors.lastname: Peluso
authors.forename: Anna
authors.initials: A
authors.lastname: Marabotti
authors.forename: Angelo
authors.initials: A
authors.lastname: Facchiano
authors.forename: Giovanna
authors.initials: G
authors.lastname: Cacciapuoti
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020134:Catalytic Domain; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004795:Enzyme Stability; D019766:Genes, Archaeal; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011684:Purine Nucleosides / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D048229:Sulfolobus solfataricus / Q000201:enzymology* / Q000235:genetics; D013816:Thermodynamics
chemical_list: D017931:DNA Primers; D011684:Purine Nucleosides; D011994:Recombinant Proteins; D009699:N-Glycosyl Hydrolases