NMR investigation of ferricytochrome
            <i>c</i>
            unfolding: Detection of an equilibrium unfolding intermediate and residual structure in the denatured state

Russell, Brandy S.; Melenkivitz, Rory; Bren, Kara L.

doi:10.1073/pnas.150239397

Cited by 105 publications

(176 citation statements)

References 43 publications

(74 reference statements)

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“…The appearance of a new wave (wave II) at potentials approximately 0.5 V lower than that of wave I (Fig. 1, Tables 2, 3 and 4) most likely corresponds to the formation of a new conformer with an altered heme iron axial coordination [14,[22][23][24].…”

Section: Discussionmentioning

confidence: 96%

“…The properties of wave II suggest its assignment to a species subjected to substitution of the axial ligand Met80 by a harder base such as a nitrogen atom of a histidine or lysine residue. At high urea concentrations ([urea] C 8 M) it is well established that a bishistidinate form of the cytochrome c is the prevailing species [14,22,23] while at low urea concentrations (4 \ [urea] \ 8) an equilibrium between a His-Lys form and the bis-histidinate one has been proposed [14]. The more basic character of the nitrogen atom(s) of the histidine (or lysine) ligand compared to the thioether sulfur of the native methionine stabilizes the ferriheme and is likely to be mainly responsible for the dramatic decrease in E°0 value of wave II as compared to wave I.…”

Section: Discussionmentioning

confidence: 99%

“…The molecular determinants of the formal reduction potential E°0, along with effects of temperature, ionic strength, solvent composition, pH-induced conformational changes and ligand binding have been investigated extensively [4][5][6][7][8]. Significant insight into the functional properties of cytochrome c can also be gained from the investigation of the folding and unfolding process, in particular the mechanisms controlling the formation of the functionally active three-dimensional structure of the protein [9][10][11][12][13][14]. Myer et al [15] proposed a denaturation mechanism summarized by the scheme:…”

Section: Introductionmentioning

confidence: 99%

“…The transition X 2 D involves rupture of the Fe-S(Met80) bond, its substitution with a linkage to another His residue (at neutral pH) or an H 2 O molecule (at acidic pH), loosening of the tryptophan-heme domain and an almost complete rearrangement of the polypeptide conformation of the protein. More recently, however, more complicated mechanisms have been proposed [14,[16][17][18][19][20][21]. Concerted unfolding units (foldons) have been claimed to determine the folding-unfolding behavior of cytochrome c [16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…In particular the N-yellow X loop (residues 40-57) is suggested to be involved in the first step of the unfolding pathway [21]. Moreover, on the basis of 1 H NMR measurements, a non-native form attributed to the replacement of Met80 with one lysine side chain has been observed under mild (partially) denaturing conditions [14]. This form has been proposed to originate the bis-histidinate form under stronger denaturing conditions.…”

Section: Introductionmentioning

confidence: 99%

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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: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Redox thermodynamics of cytochromes c subjected to urea induced unfolding

et al. 2009

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Nuclear Magnetic Resonance ( NMR ) Spectroscopy of Metallobiomolecules

Bren

2005

Encyclopedia of Inorganic Chemistry

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Nuclear magnetic resonance (NMR) spectroscopy provides information on the structure and dynamics of metallobiomolecules at atomic resolution. A range of metal‐binding sites in biomolecules can be studied by NMR, although the methods used require consideration of the properties of the metal site. Diamagnetic metal‐binding sites are probed using conventional NMR approaches appropriate for analyzing interactions between ions and macromolecules. Weak metal binding as is common in RNAs may require use of mimics that bind more strongly and/or that provide a specific spectroscopic handle. Paramagnetic metals induce hyperfine shifting and linebroadening that serve as signals of metal binding, but may also require adjustments to standard NMR methodologies. Hyperfine shifting takes place through scalar or dipolar mechanisms, and these effects in turn reveal details of metal site structure and metal electronic structure. Paramagnetic effects on chemical shifts are also used to refine structures of metallobiomolecules. Resonance broadening resulting from the hyperfine interaction is related to unpaired electron–nucleus distance as well as properties of the metal ion and thus can be a restraint on structure. The high magnetic anisotropy of some paramagnetic biomolecules can cause the molecule to take a preferential orientation within the applied magnetic field to allow observation of residual dipolar couplings, which reveal relative angular orientations of bond vectors. The study of the many effects of paramagnetic centers on NMR spectra has advanced the field of biomolecular solution structure determination as these efforts have introduced new restraints used in calculating structures. NMR is also valuable for analyzing biomolecule dynamics and chemical exchange processes. A related application is analysis of interactions between metallobiomolecules and ligands, or other macromolecules. Application of NMR to metallobiomolecules has provided a means to study phenomena difficult to observe using other methods such as interactions between proteins, electron self‐exchange reactions, and biomolecule dynamics over a wide range of time scales. NMR methodology continues to advance rapidly and is expected to continue to exert a large influence on our understanding of metal sites in biomolecules.

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Nuclear Magnetic Resonance ( NMR ) Spectroscopy of Metallobiomolecules

Bren¹

2011

Encyclopedia of Inorganic and Bioinorganic Chemistry

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NMR investigation of ferricytochrome c unfolding: Detection of an equilibrium unfolding intermediate and residual structure in the denatured state

Cited by 105 publications

References 43 publications

Redox thermodynamics of cytochromes c subjected to urea induced unfolding

Redox thermodynamics of cytochromes c subjected to urea induced unfolding

Nuclear Magnetic Resonance ( NMR ) Spectroscopy of Metallobiomolecules

Nuclear Magnetic Resonance ( NMR ) Spectroscopy of Metallobiomolecules

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