title: An obligatory intermediate in the folding pathway of cytochrome c552 from Hydrogenobacter thermophilus.
abstract: The folding mechanism of many proteins involves the population of partially organized structures en route to the native state. Identification and characterization of these intermediates is particularly difficult, as they are often only transiently populated and may play different mechanistic roles, being either on-pathway productive species or off-pathway kinetic traps. Following different spectroscopic probes, and employing state-of-the-art kinetic analysis, we present evidence that the folding mechanism of the thermostable cytochrome c552 from Hydrogenobacter thermophilus does involve the presence of an elusive, yet compact, on-pathway intermediate. Characterization of the folding mechanism of this cytochrome c is particularly interesting for the purpose of comparative folding studies, because H. thermophilus cytochrome c552 shares high sequence identity and structural homology with its homologue from the mesophilic bacterium Pseudomonas aeruginosa cytochrome c551, which refolds through a broad energy barrier without the accumulation of intermediates. Analysis of the folding kinetics and correlation with the three-dimensional structure add new evidence for the validity of a consensus folding mechanism in the cytochrome c family.
authors.affiliation: Istituto Pasteur-Fondazione Cenci Bolognetti and Istituto di Biologia e Patologia Molecolari del CNR, Dipartimento di Scienze Biochimiche, Università di Roma La Sapienza, P. le A. Moro 5, 00185, Roma Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Travaglini-Allocatelli
authors.forename: Stefano
authors.initials: S
authors.lastname: Gianni
authors.forename: Vikash K
authors.initials: VK
authors.lastname: Dubey
authors.forename: Alessandro
authors.initials: A
authors.lastname: Borgia
authors.forename: Adele
authors.initials: A
authors.lastname: Di Matteo
authors.forename: Daniele
authors.initials: D
authors.lastname: Bonivento
authors.forename: Francesca
authors.initials: F
authors.lastname: Cutruzzolà
authors.forename: Kara L
authors.initials: KL
authors.lastname: Bren
authors.forename: Maurizio
authors.initials: M
authors.lastname: Brunori
mesh_terms: D001419:Bacteria / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003574:Cytochrome c Group / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry; D007700:Kinetics; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D003574:Cytochrome c Group; D005290:Ferric Compounds; C022302:cytochrome C-552