1996
DOI: 10.1016/0014-5793(96)00627-8
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Abstract: Cooperativity between redox and protonation centres is known to be crucial for the function of complex proteins, but it is often difficult to describe in terms of thermodynamic parameters. Cytochrome c3 is a good model for these studies since, while retaining the overall complexity of larger systems, it is suitable for detailed crystallographic and spectroscopic studies. Assignment of the haem substituent NMR resonances, together with NMR redox titrations of cytochrome c3 from D.desulfuricans ATCC 27774, was u… Show more

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Cited by 28 publications
(24 citation statements)
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References 26 publications
(39 reference statements)
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“…The entire data set is fitted well and, although the signals of methyl groups 18 1 of haems I and II in stage 1 appear to have larger deviations, this is a consequence of relatively large error bars resulting from linewidths typically greater than 1 ppm at half height. The order of oxidation of the four haems can be determined immediately from these plots, and at pH 8 it is the same as that reported previously at 275 K. [24] However, it is now clear that haems I and II change their order of oxidation twice in the experimental pH range, as can be appreciated from the marked bell-shaped pH dependence of their oxidised fractions at stage 1, which is caused by the combined effects of two different acid ± base centres with different pK a values. The presence of these two redox-linked acid ± base centres is not readily apparent from the results of the redox titrations followed by visible spectroscopy alone ( Figure 2).…”
Section: Resultssupporting
confidence: 51%
See 1 more Smart Citation
“…The entire data set is fitted well and, although the signals of methyl groups 18 1 of haems I and II in stage 1 appear to have larger deviations, this is a consequence of relatively large error bars resulting from linewidths typically greater than 1 ppm at half height. The order of oxidation of the four haems can be determined immediately from these plots, and at pH 8 it is the same as that reported previously at 275 K. [24] However, it is now clear that haems I and II change their order of oxidation twice in the experimental pH range, as can be appreciated from the marked bell-shaped pH dependence of their oxidised fractions at stage 1, which is caused by the combined effects of two different acid ± base centres with different pK a values. The presence of these two redox-linked acid ± base centres is not readily apparent from the results of the redox titrations followed by visible spectroscopy alone ( Figure 2).…”
Section: Resultssupporting
confidence: 51%
“…[24] NMR spectroscopy: Samples containing 1 ± 2 mM of protein and 0.1 M potassium chloride in aqueous solution were poised at partially oxidised conditions and at different solution pH values using the procedures reported in the literature. [13] Measurements were performed in the pH range 4.6 ± 8.6 (meter readings not corrected for the isotope effect).…”
Section: Methodsmentioning
confidence: 99%
“…The pH values were adjusted with minimal amounts either of NaO'H or 'HC1 and are quoted as meter readings uncorrected for the isotope effect. The reduced and intermediate stages of oxidation were obtained as previously described Turner et al, 1996;Louro et al, 1996b).…”
Section: Methodsmentioning
confidence: 99%
“…A series of two-dimensional NMR studies has extended the number of both haem and non-haem proton assignments in the tetrahaem cytochromes c1 in reduced (diamagnetic) and in oxidised (paramagnetic) forms and allowed the cross-assignment of the individual haem redox potentials to the known X-ray structures Turner et al, 1992;Coutinho et al, 1992Coutinho et al, , 1993Coutinho et al, , 1995Park et al, 1991aPark et al, , b, 1996Piprra-Pereira et al, 1993;Sola and Cowan, 1992;Louro et al, 1996b). In recent studies of ferricytochroine c3 from DvH, the "C resonances of the haem substituents were also identified .…”
mentioning
confidence: 99%
“…At high pH values, the Dv cyt c 3 shows a typical low-spin NMR spectrum, with the chemical shifts of the heme methyl groups situated at 10-30 ppm and presenting narrow line widths. On the other hand, the NMR spectrum of the totally reduced form has diamagnetic properties leading to the conclusion of the presence of a low-spin form [22]. With the decrease of the pH values, these resonances are substituted by enlarged bands, with chemical shifts in the low field region of 80 ppm that indicate a transition to a high spin state (S = 5/2), supporting the hypothesis of the axial ligand protonation.…”
Section: H Nmr and Epr Spectroscopiesmentioning
confidence: 70%