Folding of horse cytochrome c in the reduced state11Edited by C. R. Matthews

Bhuyan, Abani K.; Udgaonkar, Jayant B.

doi:10.1006/jmbi.2001.4993

Cited by 78 publications

(110 citation statements)

References 81 publications

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“…The absence and/or the low intensity of the anodic peak could be therefore related also to the instability of both the reduced His-Lys and bis-histidinate forms of the cytochrome c which transform rapidly into the reduced His-Met ligated form. This is not surprising since the reduced form of cytochrome c in solution retains its His-Met ligation up to 9 M urea [22,45] and a similar behavior has been already observed for the ''alkaline'' form of cytochrome c in solution, in which the axial ligand Met80 is substituted by a lysine ligand [33,46].…”

Section: Discussionsupporting

confidence: 67%

Redox thermodynamics of cytochromes c subjected to urea induced unfolding

et al. 2009

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The thermodynamics of the electron transfer (ET) process for beef heart and yeast cytochromes c and the Lys72Ala/Lys73Ala/Lys79Ala mutant of the latter species subjected to progressive urea-induced unfolding was determined electrochemically. The results indicate the presence of at least three protein forms which were assigned to a low-temperature and a high-temperature HisMet intermediate species and a bis-histidinate form (although the presence of a His-Lys form cannot be excluded). The much lower E°0 value of the bis-histidinate conformer as compared to His-Met ligated species is largely determined by the enthalpic contribution induced by axial ligand substitution. The biphasic E°0 versus T profile for the His-Met species is due to a difference in reduction entropy between the conformers at low and high temperatures. Enthalpy-entropy compensation phenomena for the reduction reaction at varying urea concentration for all the forms of the investigated cytochromes c were addressed and discussed.

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Section: Discussionsupporting

confidence: 67%

Redox thermodynamics of cytochromes c subjected to urea induced unfolding

et al. 2009

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“…Three-state folding occurs when a native-like intermediate additionally contains some slowly repaired misfolding error. In agreement, folding intermediates for many proteins are seen to be partial replicas of the native protein, whether they are kinetically populated or not, and the kinetically blocked forms are also seen to contain some significant misfolding (Kiefhaber et al 1992;Dobson et al 1994;Elöve et al 1994;Muñoz et al 1994;Sosnick et al 1994Sosnick et al , 1996Weissman and Kim 1995;Silow and Oliveberg 1997;Bai 1999;Bilsel et al 1999;Bhuyan and Udgaonkar 2001;Capaldi et al 2002;Wallace and Matthews 2002;Krishna et al 2003aKrishna et al , 2004Bollen et al 2004;Rojsajjakul et al 2004;Religa et al 2005;Wintrode et al 2005;Nishimura et al 2006).…”

Section: Three-state Foldingmentioning

confidence: 71%

A unified mechanism for protein folding: Predetermined pathways with optional errors

Mallela

Englander

2007

Protein Science

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There is a fundamental conflict between two different views of how proteins fold. Kinetic experiments and theoretical calculations are often interpreted in terms of different population fractions folding through different intermediates in independent unrelated pathways (IUP model). However, detailed structural information indicates that all of the protein population folds through a sequence of intermediates predetermined by the foldon substructure of the target protein and a sequential stabilization principle. These contrary views can be resolved by a predetermined pathway-optional error (PPOE) hypothesis. The hypothesis is that any pathway intermediate can incorporate a chance misfolding error that blocks folding and must be reversed for productive folding to continue. Different fractions of the protein population will then block at different steps, populate different intermediates, and fold at different rates, giving the appearance of multiple unrelated pathways. A test of the hypothesis matches the two models against extensive kinetic folding results for hen lysozyme which have been widely cited in support of independent parallel pathways. The PPOE model succeeds with fewer fitting constants. The fitted PPOE reaction scheme leads to known folding behavior, whereas the IUP properties are contradicted by experiment. The appearance of a conflict with multipath theoretical models seems to be due to their different focus, namely on multitrack microscopic behavior versus cooperative macroscopic behavior. The integration of three well-documented principles in the PPOE model (cooperative foldons, sequential stabilization, optional errors) provides a unifying explanation for how proteins fold and why they fold in that way.Keywords: protein folding; misfolding; foldons; sequential stabilization; optional error; predetermined pathway; lysozyme Detailed structural information obtained from hydrogen exchange (HX) studies of cytochrome c (Cyt c) and related studies with other proteins support a classical view of protein folding in which all of the molecules in a refolding population fold through essentially the same intermediate structures (Chamberlain and Marqusee 2000;Englander 2000;Maity et al. 2005). The pathway constructs the native protein by the stepwise addition of the cooperative folding units of the native structure, called foldons. The order of pathway steps is guided by a sequential stabilization process in which prior native-like structure templates the formation of subsequent complementary structure. Thus the folding pathway is determined by the same cooperative interactions that determine the target native structure. The pathway may be linear or may branch at any step as directed by the logic of the sequential stabilization process (Krishna et al. 2006 449quite differently, in terms of independent unrelated pathways (IUP model). Proteins can fold in a simple two-state way with only the unfolded (U) and native (N) states significantly populated, or in a multistate way with one or more intermediates (...

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“…The appearance of the anodic counterpart of wave II only for high scan rates is probably related to the instability of the reduced bishistidine form which transforms rapidly into the corresponding His-Met form, denoted as the B1 state [38]. This is not surprising since the reduced form of cytochrome c in solution retains its His-Met ligation up to 9 M urea [41,42]. The transition from the ferrous U[6cLS] to the ferric B1 state requires the removal of the His33 (His26) ligand from the haem, rebinding of Met80 and the movement of the peptide segment including the His ligand away from the haem pocket to its ''native'' position.…”

Section: Identification Of the Adsorbed Speciesmentioning

confidence: 99%

The impact of urea-induced unfolding on the redox process of immobilised cytochrome c

et al. 2010

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We have studied the effect of urea-induced unfolding on the electron transfer process of yeast iso-1-cytochrome c and its mutant K72AK73AK79A adsorbed on electrodes coated by mixed 11-mercapto-1-undecanoic acid/ 11-mercapto-1-undecanol self-assembled monolayers. Electrochemical measurements, complemented by surface enhanced resonance Raman studies, indicate two distinct states of the adsorbed proteins that mainly differ with respect to the ligation pattern of the haem. The native state, in which the haem is axially coordinated by Met80 and His18, displays a reduction potential that slightly shifts to negative values with increasing urea concentration. At urea concentrations higher than 6 M, a second state prevails in which the Met80 ligand is replaced by an additional histidine residue. This structural change in the haem pocket is associated with an approximately 0.4 V shift of the reduction potential to negative values. These two states were found for both the wild-type protein and the mutant in which lysine residues 72, 73 and 79 had been substituted by alanines. The analysis of the reduction potentials, the reaction enthalpies and entropies as well as the rate constants indicates that these three lysine residues have an important effect on stabilising the protein structure in the adsorbed state and facilitating the electron transfer dynamics.

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Folding of horse cytochrome c in the reduced state11Edited by C. R. Matthews

Cited by 78 publications

References 81 publications

Redox thermodynamics of cytochromes c subjected to urea induced unfolding

Redox thermodynamics of cytochromes c subjected to urea induced unfolding

A unified mechanism for protein folding: Predetermined pathways with optional errors

The impact of urea-induced unfolding on the redox process of immobilised cytochrome c

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