The Met80Ala and Met80Ala/Tyr67Ala variants of S. cerevisiae iso-1 cytochrome c (ycc ) immobilized on a decane-1-thiol coated gold electrode subjected to the denaturing action of urea were studied through variable temperature cyclic voltammetry and Surface-Enhanced Resonance Raman spectroscopy (SERRS). We found that the His/OH - axial heme iron coordination in both variants is unaffected by urea up to 7 M, although some conformational changes occur that increase exposure of the heme center to solvent. The thermodynamics of the unfolding process were determined with an unprecedented approach, which can be of general use for electroactive proteins. The free energy of unfolding for both variants includes relevant entropic contributions and is lower than that for the species carrying an intact Met/His coordination, consistent with the role of the axial Fe-(S)Met bond and the H-bond network involving Tyr67 in stabilizing the polypeptide matrix in the heme crevice. Their lower conformational stability results in a different interaction with the MUA/MU SAM compared to the His/Met ycc forms. Denaturation invariably slows down the heterogeneous electron transfer process, but its effect on the activation enthalpy and pre-exponential factor differs for the species with and without His/Met axial heme ligation. In particular, urea unfolding of the M80A and M80A/Y67A mutants lowers the structural restraint to the heterogeneous ET. Here we show that removal of the Met ligand and an increased accessibility of the heme center to solvent through partial protein unfolding– which mimic the molecular stress experienced by mammalian cytochromes c upon binding to cardiolipin in the early events of apoptosis - add up to transform cytochrome c into an efficient electrocatalyst toward the reduction of hydrogen peroxide and nitrite.

Urea-induced denaturation of immobilized yeast iso-1 cytochrome c: role of Met80 and Tyr67 in the thermodynamics of unfolding and promotion of pseudoperoxidase and nitrite reductase activities / Lancellotti, Lidia; Borsari, Marco; Bellei, Marzia; Bonifacio, Alois; Bortolotti, Carlo Augusto; DI ROCCO, Giulia; Ranieri, Antonio; Sola, Marco; Battistuzzi, Gianantonio. - In: ELECTROCHIMICA ACTA. - ISSN 0013-4686. - 10:363(2020), pp. 1-11. [10.1016/j.electacta.2020.137237]

Urea-induced denaturation of immobilized yeast iso-1 cytochrome c: role of Met80 and Tyr67 in the thermodynamics of unfolding and promotion of pseudoperoxidase and nitrite reductase activities

Lidia Lancellotti;Marco Borsari;Marzia Bellei;Carlo Augusto Bortolotti;Giulia Di Rocco;Antonio Ranieri;Marco Sola;Gianantonio Battistuzzi
2020

Abstract

The Met80Ala and Met80Ala/Tyr67Ala variants of S. cerevisiae iso-1 cytochrome c (ycc ) immobilized on a decane-1-thiol coated gold electrode subjected to the denaturing action of urea were studied through variable temperature cyclic voltammetry and Surface-Enhanced Resonance Raman spectroscopy (SERRS). We found that the His/OH - axial heme iron coordination in both variants is unaffected by urea up to 7 M, although some conformational changes occur that increase exposure of the heme center to solvent. The thermodynamics of the unfolding process were determined with an unprecedented approach, which can be of general use for electroactive proteins. The free energy of unfolding for both variants includes relevant entropic contributions and is lower than that for the species carrying an intact Met/His coordination, consistent with the role of the axial Fe-(S)Met bond and the H-bond network involving Tyr67 in stabilizing the polypeptide matrix in the heme crevice. Their lower conformational stability results in a different interaction with the MUA/MU SAM compared to the His/Met ycc forms. Denaturation invariably slows down the heterogeneous electron transfer process, but its effect on the activation enthalpy and pre-exponential factor differs for the species with and without His/Met axial heme ligation. In particular, urea unfolding of the M80A and M80A/Y67A mutants lowers the structural restraint to the heterogeneous ET. Here we show that removal of the Met ligand and an increased accessibility of the heme center to solvent through partial protein unfolding– which mimic the molecular stress experienced by mammalian cytochromes c upon binding to cardiolipin in the early events of apoptosis - add up to transform cytochrome c into an efficient electrocatalyst toward the reduction of hydrogen peroxide and nitrite.
2020
11-ott-2020
10
363
1
11
Urea-induced denaturation of immobilized yeast iso-1 cytochrome c: role of Met80 and Tyr67 in the thermodynamics of unfolding and promotion of pseudoperoxidase and nitrite reductase activities / Lancellotti, Lidia; Borsari, Marco; Bellei, Marzia; Bonifacio, Alois; Bortolotti, Carlo Augusto; DI ROCCO, Giulia; Ranieri, Antonio; Sola, Marco; Battistuzzi, Gianantonio. - In: ELECTROCHIMICA ACTA. - ISSN 0013-4686. - 10:363(2020), pp. 1-11. [10.1016/j.electacta.2020.137237]
Lancellotti, Lidia; Borsari, Marco; Bellei, Marzia; Bonifacio, Alois; Bortolotti, Carlo Augusto; DI ROCCO, Giulia; Ranieri, Antonio; Sola, Marco; Battistuzzi, Gianantonio
File in questo prodotto:
File Dimensione Formato  
ElectochimicaActa2020.pdf

Accesso riservato

Descrizione: manoscritto pubblicato
Tipologia: Versione pubblicata dall'editore
Dimensione 1.6 MB
Formato Adobe PDF
1.6 MB Adobe PDF   Visualizza/Apri   Richiedi una copia
Pubblicazioni consigliate

Licenza Creative Commons
I metadati presenti in IRIS UNIMORE sono rilasciati con licenza Creative Commons CC0 1.0 Universal, mentre i file delle pubblicazioni sono rilasciati con licenza Attribuzione 4.0 Internazionale (CC BY 4.0), salvo diversa indicazione.
In caso di violazione di copyright, contattare Supporto Iris

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/1226076
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 10
  • ???jsp.display-item.citation.isi??? 9
social impact