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Turner, DL, Salgueiro CA, Schenkels P, Legall J, Xavier AV.  1995.  Carbon-13 NMR studies of the influence of axial ligand orientation on haem electronic structure. Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology. 1246(1):24-28. AbstractWebsite

Three-quarters of the carbon-13 resonances of nuclei attached to the four haems of Desulfovibrio vulgaris ferricytochrome c3 are assigned. Preliminary analysis of their Fermi contact interactions shows that the shifts are directly related to the orientation of both of the axial histidine ligands in each case and the approach can therefore be used to obtain structural information in other cytochromes with bis-histidinyl coordination. The implications for the control of redox potential in cytochromes are discussed.

Turner, DL, Salgueiro CA, Catarino T, Legall J, Xavier AV.  1994.  Homotropic and heterotropic cooperativity in the tetrahaem cytochrome c3 from Desulfovibrio vulgaris. Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1187(2):232-235. AbstractWebsite

The thermodynamic parameters which govern the homotropic (e−/e−) and heterotropic (e−/H+) cooperativity in the tetrahaem cytochrome c3 isolated from Desulfovibrio vulgaris (Hildenborough) were determined, using the paramagnetic shifts of haem methyl groups in the NMR spectra of intermediate oxidized states at different pH levels. A model is put forward to explain how the network of positive and negative cooperativities between the four haems and acid/base group(s) enables the protein to achieve a proton-assisted 2e− step.

Salgueiro, CA, Turner DL, Santos H, Legall J, Xavier AV.  1992.  Assignment of the redox potentials to the four haems in Desulfovibrio vulgaris cytochrome c3 by 2D-NMR. FEBS Letters. 314(2):155-158. AbstractWebsite

Using 2D-NMR the four haems of Desulfovibrio vulgaris (Hildenborough) cytochromes, within the X-ray structure were fully cross-assigned according to their redox potential. The strategy used was based on a complete network of chemical exchange connectivities between the NMR signals obtained for all oxidation levels to the corresponding ones in the fully reduced spectrum [1992, Eur. J. Biochem., in press]. This unequivocal cross-assignment disagrees within earlier results obtained for the similar protein from Desulfovibrio vulgaris (Miyazaki F.) [1991, FEBS Lett. 285, 149–151]

Turner, DL, Salgueiro CA, Legall J, Xavier AV.  1992.  Structural studies of Desulfovibrio vulgaris ferrocytochrome c3 by two-dimensional NMR. European Journal of Biochemistry. 210(3):931-936. AbstractWebsite

Two-dimensional NMR has been used to make specific assignments for the four haems in Desulfovibrio vulgaris (Hildenborough) ferrocytochrome c3 and to determine their haem core architecture. The NMR signals from the haem protons were assigned according to type using two-dimensional NMR experiments which led to four sets of signals, one for each of the haems. Specific assignments were obtained by calculating the ring current shifts which arise from other haems and aromatic residues. Observation of interhaem NOEs confirmed the assignments and established that the relative orientation of the haems is identical to that found in the crystal structure of D. vulgaris (Miyazaki F.) ferricytochrome c3. Assignments were also made for all the aromatic residues except for the haem ligands and F20, which is shifted under the main envelope of signals. The NOEs observed between these aromatic protons and haem protons confirm the similarity between the structures in solution and in the crystal. The assignments reported here are the basis for the cross-assignments of the four microscopic haem redox potentials to specific haems in the protein structure.