title: Identification of an active dimeric intermediate populated during the unfolding process of the cambialistic superoxide dismutase from Streptococcus mutans.
abstract: Superoxide dismutases are enzymes that protect biological systems against oxidative damage caused by superoxide radicals. In this paper, a detailed characterization is presented on the stability of SmSOD, the dimeric cambialistic superoxide dismutase from the dental pathogenic microorganism Streptococcus mutans, towards temperature and guanidine hydrochloride. Thermal and chemical denaturations were investigated by means of circular dichroism, fourth-derivative UV spectroscopy and fluorescence measurements. Data indicate that SmSOD is endowed with a significant thermostability and that both its thermal and guanidine hydrochloride-induced unfolding processes occur through a three-state model, characterized by a catalytically active dimeric intermediate species. To our knowledge, SmSOD is the smallest known dimeric protein that populates a well-structured active dimeric rather than a monomeric intermediate during unfolding processes.
authors.affiliation: Dipartimento di Chimica, Università di Napoli Federico II, Complesso Universitario Monte S. Angelo, Via Cinthia, I-80126 Naples, Italy; Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, I-80134 Naples, Italy.
authors.forename: Antonello
authors.initials: A
authors.lastname: Merlino
authors.forename: Irene
authors.initials: I
authors.lastname: Russo Krauss
authors.forename: Bianca
authors.initials: B
authors.lastname: Rossi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Vergara
authors.forename: Alberto
authors.initials: A
authors.lastname: De Vendittis
authors.forename: Salvatore
authors.initials: S
authors.lastname: Marco
authors.forename: Emmanuele
authors.initials: E
authors.lastname: De Vendittis
authors.forename: Filomena
authors.initials: F
authors.lastname: Sica
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D017510:Protein Folding; D013295:Streptococcus mutans / Q000201:enzymology*; D013482:Superoxide Dismutase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D013482:Superoxide Dismutase