Carbon-13 NMR studies of the influence of axial ligand orientation on haem electronic structure

Turner, David L.; Salgueiro, Carlos A.; Schenkels, P.; LeGall, Jean; Xavier, António V.

doi:10.1016/0167-4838(94)00175-g

Cited by 58 publications

(69 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the case of PpcA, only four heme methyl signals could be assigned with confidence to their final position in the paramagnetic protein: 2 1 H-13 C-HSQC (Fig. 1) NMR experiments, following the strategy first described for Desulfovibrio vulgaris (Hildenborough) cytochrome c 3 [21,28]. All assignments are listed in Table 1.…”

Section: Resonance Assignmentmentioning

confidence: 99%

Orientation of the axial ligands and magnetic properties of the hemes in the triheme ferricytochrome PpcA from G. sulfurreducens determined by paramagnetic NMR

Morgado¹,

Saraiva²,

Louro³

et al. 2010

FEBS Letters

Self Cite

View full text Add to dashboard Cite

a b s t r a c tThe geometry of the axial ligands of the hemes in the triheme cytochrome PpcA from Geobacter sulfurreducens was determined in solution for the ferric form using the unambiguous assignment of the NMR signals of the a-substituents of the hemes. The paramagnetic 13 C shifts of the hemes can be used to define the heme electronic structure, the geometry of the axial ligands, and the magnetic susceptibility tensor. The latter establishes the magnitude and geometrical dependence of the pseudocontact shifts, which are crucial to warrant reliable structural constraints for a detailed structural characterization of this paramagnetic protein in solution.

show abstract

Section: Resonance Assignmentmentioning

confidence: 99%

Orientation of the axial ligands and magnetic properties of the hemes in the triheme ferricytochrome PpcA from G. sulfurreducens determined by paramagnetic NMR

Morgado¹,

Saraiva²,

Louro³

et al. 2010

FEBS Letters

Self Cite

View full text Add to dashboard Cite

show abstract

“…cytochrome c, is a small (=14 m a ) , monomeric tetrahaem protein which exhibits cooperativity between the four haems and acidmase group(s): the haem redox potentials are pH dependent (redox-Bohr effect) and each haem redox potential is dependent on the oxidation state of the other three haems (redox interaction potentials) [4-61. Due to its small size and the fact that the haems are diamagnetic in the reduced state and paramagnetic in the oxidised one, NMR is particularly well suited to characterise this protein from the structural and thermodynamic point of view [4,[7][8][9][10][11][12][13][14][15].…”

mentioning

confidence: 99%

NMR Studies of Cooperativity in the Tetrahaem Cytochrome c₃ from Desulfovibrio vulgaris

Turner

Salgueiro

Catarino

et al. 1996

European Journal of Biochemistry

Self Cite

100

204

View full text Add to dashboard Cite

The thermodynamic properties of the Desulfovibrio vulgaris (Hildenborough) tetrahaem cytochrome c3 (Dvc,) are rationalised by a model which involves both homotropic (e-/e-) and heterotropic (e-/H+) cooperativity. The paramagnetic shifts of a methyl group from each haem of the DVC, have been determined in each stage of oxidation at several pH values by means of two-dimensional exchange NMR. The thermodynamic parameters are obtained by fitting the model to the NMR data and to redox titrations followed by visible spectroscopy. They show significant positive cooperativity between two of the haems whereas the remaining interactions appear to be largely electrostatic in origin. These parameters imply that the protein undergoes a proton-assisted two-electron transfer which can be used for energy transduction. Comparison with the crystal structure together with measurement of the kinetics of proton exchange suggest that the pH dependence is mediated by a charged residue(s) readily acessible to the solvent and close to haem I.Keywords: cooperativity ; energy transduction ; multiheme cytochrome ; NMR ; redox-Bohr.The functional cooperativity between different regions of some proteins [ l ] is a fundamental property to control and coordinate important chemical events in the living cell. Although the molecular basis for the fine regulation of several types of cooperativity mechanisms has been successfully established [2], little is known about the structural basis for electron/electron and electron/proton cooperativities and their role either in electron transfer or in energy transduction [3].Desulfovibrio spp. cytochrome c, is a small (=14 m a ) , monomeric tetrahaem protein which exhibits cooperativity between the four haems and acidmase group(s): the haem redox potentials are pH dependent (redox-Bohr effect) and each haem redox potential is dependent on the oxidation state of the other three haems (redox interaction potentials) [4-61. Due to its small size and the fact that the haems are diamagnetic in the reduced state and paramagnetic in the oxidised one, NMR is particularly well suited to characterise this protein from the structural and thermodynamic point of view [4,[7][8][9][10][11][12][13][14][15].Furthermore, several X-ray structures are available for cytochromes c3 from Desulfovibrio spp. [16-231.The thermodynamic properties of cytochrome c, have been analysed by previous NMR studies [4,5,8,15, 241. In the first of these studies an NMR data set obtained at two discrete pH values for Desulfovibrio gigas cytochrome c, was used to calculate nine parameters (three relative microscopic redox potentials and six haem-haem redox interactions) for each pH value, independently treated. The redox interaction potentials were fixed according to the maximum concentration reached by the intermediate oxidation stages (defined according to the number of oxidised haems) in redox titrations followed by NMR [4]. Using the same NMR data set, a second study proposed a model with 21 parameters in which the four haem redox potentials ...

show abstract

“…Preliminary analysis of data from the four bis-His haems of cytochrome c3 supports a relationship of this form [32], but it fails to explain the difference between the splittings observed for horse cytochrome c and cytochrome c551 since j3 is about 60" in each case according to the crystal structures. Much of the anomaly could be explained if the errors in the crystal structures of the two proteins happened to have opposite senses.…”

Section: The Relationship Between Molecular Orbitals and G Valuesmentioning

confidence: 82%

“…the energy of the iron d orbitals increases in relation to that of the porphin orbitals), the character of the highest partially filled molecular orbital changes from partial back donation from the highest filled porphin orbital to delocalisation from the iron into the lowest antibonding porphin orbital [21] and so a dramatic variation would be observed in the Fermi contact shifts. The sum of the I3C shifts shows little variation in the cytochromes which have been examined so far, including bis-His cytochromes c and b [32]. The values of aFe obtained for horse cytochrome c and P. aeruginosa cytochrome cS5!…”

Section: The Relationship Between Molecular Orbitals and G Valuesmentioning

confidence: 94%

Determination of Haem Electronic Structure in His‐Met Cytochromes c by ¹³C‐NMR

Turner

1995

European Journal of Biochemistry

Self Cite

View full text Add to dashboard Cite

The assignment of 13C resonances of nuclei a to the haem in horse ferricytochrome c is completed and the Fenni contact shifts are evaluated at 30°C and 50°C using empirical magnetic susceptibility tensors to correct for dipolar interactions. The Fermi contact shifts are fitted to a model of molecular orbitals of e, symmetry, which are subject to a rhombic perturbation. A similar analysis is performed using published data for Pseudomonas aeruginosa cytochrome c551. The relationship between the orientation of the effective g tensor and that of the rhombic perturbation in these proteins is shown to agree with theoretical predictions. A comparison between the orientation of the rhombic perturbations and the crystal structures of horse cytochrome c and I? aeruginosa cytochrome cS5, reveals that the orientation of the histidine and methionine axial ligands dominates the rhombic perturbation and that the two ligands have approximately equal influence. The magnitude of the perturbation shows that the orientation of the axial ligands has little effect on the haem redox potential. However, the relationship that is established between the magnetic susceptibility tensor, the partially filled haem molecular orbitals, and the orientation of the haem ligands offers a new source of precise structural information.

show abstract

Carbon-13 NMR studies of the influence of axial ligand orientation on haem electronic structure

Cited by 58 publications

References 20 publications

Orientation of the axial ligands and magnetic properties of the hemes in the triheme ferricytochrome PpcA from G. sulfurreducens determined by paramagnetic NMR

Orientation of the axial ligands and magnetic properties of the hemes in the triheme ferricytochrome PpcA from G. sulfurreducens determined by paramagnetic NMR

NMR Studies of Cooperativity in the Tetrahaem Cytochrome c₃ from Desulfovibrio vulgaris

Determination of Haem Electronic Structure in His‐Met Cytochromes c by ¹³C‐NMR

Contact Info

Product

Resources

About

Carbon-13 NMR studies of the influence of axial ligand orientation on haem electronic structure

Cited by 58 publications

References 20 publications

Orientation of the axial ligands and magnetic properties of the hemes in the triheme ferricytochrome PpcA from G. sulfurreducens determined by paramagnetic NMR

Orientation of the axial ligands and magnetic properties of the hemes in the triheme ferricytochrome PpcA from G. sulfurreducens determined by paramagnetic NMR

NMR Studies of Cooperativity in the Tetrahaem Cytochrome c3 from Desulfovibrio vulgaris

Determination of Haem Electronic Structure in His‐Met Cytochromes c by 13C‐NMR

Contact Info

Product

Resources

About

NMR Studies of Cooperativity in the Tetrahaem Cytochrome c₃ from Desulfovibrio vulgaris

Determination of Haem Electronic Structure in His‐Met Cytochromes c by ¹³C‐NMR