Biomedical subjects

I Bertini

Publications and source records attributed to I Bertini.

At least 73 records · Page 4Linked to original sources

PubMed1999

Simultaneous interpretation of Mössbauer, EPR and 57Fe ENDOR spectra of the [Fe4S4] cluster in the high-potential iron protein I from Ectothiorhodospira halophila.

Mössbauer spectra of the oxidized [Fe4S4]3+ and the reduced [Fe4S4]2+ clusters in the high-potential iron protein I from Ectothiorhodospira halophila were measured in a temperature range from 5 K to 240 K. EPR measurements and 57Fe electron-nuclear double resonance (ENDOR) experiments were carried out with the oxidized protein. In the oxidized state the cluster has a net spin S = 1/2 and is paramagnetic. As common in [Fe4S4]3+ clusters, the Mössbauer spectrum was simulated with two species contributing equally to the absorption area: two Fe3+ atoms couple to the "ferric-ferric" pair, and one Fe2+ and one Fe3+ atom give the "ferric-ferrous pair". For the simulation of the Mössbauer spectrum, g-values were taken from EPR measurements. A-tensor components were determined by 57Fe ENDOR experiments that turned out to be a necessary source of estimating parameters independently. In order to obtain a detailed agreement of Mössbauer and ENDOR data, electronic relaxation has to be taken into account. Relaxing the symmetry condition in a way that the electric field gradient tensor does not coincide with g- and A-tensors yielded an even better agreement of experimental and theoretical Mössbauer spectra. Spin-spin and spinlattice relaxation times were estimated by pulsed EPR; the former turned out to be the dominating mechanism at T = 5 K. Relaxation times measured by pulsed EPR and obtained from the Mössbauer fit were compared and yield nearly identical values. The reduced cluster has one additional electron and has a diamagnetic (S = 0) ground state. All the four irons are indistinguishable in the Mössbauer spectrum, indicating a mixed-valence state of Fe2.5+ for each.

Bacterial Proteins↗

PubMed1999

The solution structure of a monomeric, reduced form of human copper,zinc superoxide dismutase bearing the same charge as the native protein.

The solution structure of a mutated (Phe50Glu, Gly51Glu, Val148Lys, Ile151Lys), reduced, monomeric form of human copper,zinc superoxide dismutase (SOD; 153 amino acids) has been determined through 2237 meaningful nuclear Overhauser enhancements, out of 2492, and 43 dihedral angle constraints. A characteristic of this mutant is that of having the same overall charge as the dimeric protein, but an activity of only 20% with respect to wild-type SOD. This protein, at variance with a previously characterized monomeric form (Phe50Glu, Gly51Glu, Glu133Gln), does not contain mutations in the active site. Therefore, its characterization allows us to understand the structural changes independently induced by the monomerization and by the active site mutation. The family of 36 conformers, which have a target function with respect to the experimental constraints lower than 1.5 A2, has RMSD values with respect to the average structure of 0.94 +/- 0.14 A2 and 1.50 +/- 0.14 A2 for the backbone and the heavy atoms, respectively. The overall folding, which includes the classical eight-stranded Greek-key beta-barrel and a short alpha-helix, is very close to that of the previously characterized monomeric mutant E133QM2SOD and to that of wild-type SOD. The region involved in the subunit-subunit interactions in the dimeric protein is confirmed to be disordered in the monomeric species. It is also observed that a sizable rearrangement of the charged groups of the electrostatic loop and of Arg143 takes place in the monomeric species. The width of the active site channel, both at its entrance and at the bottleneck of the active site, is discussed in the light of the influence on the enzymatic activity and the latter with respect to the overall charge. It is also confirmed that the NH proton of His63 shields the Cu(I) from the bulk solvent, thus supporting the suggestion that superoxide may interact with the reduced metal ion in an outer-sphere fashion.

Binding Sites↗

PubMed1999

Mitochondrial cytochromes c: a comparative analysis.

The structures of 113 eukaryotic cytochrome c proteins of known sequence have been modeled in the oxidized state based on the existing crystallographic and NMR structures. The secondary structural elements and the overall three-dimensional structure were found to be maintained throughout the super-family, despite variability in the sequence of individual proteins. The iron axial ligands and their reciprocal orientation were found to be nearly universally conserved. Residues constituting the hydrophobic core of the protein are also very highly conserved or conservatively substituted. Certain surface-exposed charged as well as hydrophobic groups have also been found to be conserved to the same degree as core residues. Patterns of conservation of exposed residues identify regions of the protein that are likely to be critical for its function in electron transfer.

Amino Acid Sequence↗

PubMed1999

New applications of paramagnetic NMR in chemical biology.

The methodological accessibility to solution structure and dynamic investigation of paramagnetic metallobiomolecules has afforded the ability to tackle the redox pairs of electron transfer proteins of which at least one is paramagnetic, to study the orientation effects of high magnetic fields on paramagnetic biomolecules, and finally to study the role of metal-based cofactors in protein folding and stability.

Magnetic Resonance Spectroscopy↗

PubMed1999

Solution structure of the B form of oxidized rat microsomal cytochrome b5 and backbone dynamics via 15N rotating-frame NMR-relaxation measurements. Biological implications.

Cytochrome b5 in solution has two isomers (A and B) differing by a 180 degrees rotation of the protoporphyrin IX plane around the axis defined by the alpha and gamma meso protons. Homonuclear and heteronuclear NMR spectroscopy has been employed in order to solve the solution structure of the minor (B) form of the oxidized state of the protein and to probe its backbone dynamics in the microsecond--ms timescale in both oxidation states. A family of 40 conformers has been obtained using 1302 meaningful NOEs and 220 pseudocontact shifts and is characterized by high quality and good resolution (rmsd to the mean structure of 0.055 +/- 0.009 nm and 0.103 +/- 0.011 nm for backbone and heavy atoms, respectively). Extensive comparisons of the structural and dynamics changes associated with the A-to-B form interconversion for both oxidation states were subsequently performed. Propionate 6 experiences a redox-state-dependent reorientation as does propionate 7 in the A form. Significant insights are obtained into the role of the protein frame for efficient biological function and backbone mobility is proposed to be one of the factors that could control the reduction potential of the heme.

Animals↗

PubMed1999

A proton-NMR investigation of the fully reduced cytochrome c7 from Desulfuromonas acetoxidans. Comparison between the reduced and the oxidized forms.

The solution structure via 1H NMR of the fully reduced form of cytochrome c7 has been obtained. The protein sample was kept reduced by addition of catalytic amounts of Desulfovibrio gigas iron hydrogenase in H2 atmosphere after it had been checked that the presence of the hydrogenase did not affect the NMR spectrum. A final family of 35 conformers with rmsd values with respect to the mean structure of 8.7 +/- 1.5 nm and 12.4 +/- 1.3 nm for the backbone and heavy atoms, respectively, was obtained. A highly disordered loop involving residues 54-61 is present. If this loop is ignored, the rmsd values are 6.2 +/- 1.1 nm and 10.2 +/- 1.0 nm for the backbone and heavy atoms, respectively, which represent a reasonable resolution. The structure was analyzed and compared with the already available structure of the fully oxidized protein. Within the indetermination of the two solution structures, the result for the two redox forms is quite similar, confirming the special structural features of the three-heme cluster. A useful comparison can be made with the available crystal structures of cytochromes c3, which appear to be highly homologous except for the presence of a further heme. Finally, an analysis of the factors affecting the reduction potentials of the heme irons was performed, revealing the importance of net charges in differentiating the reduction potential when the other parameters are kept constant.

Amino Acid Sequence↗

PubMed1999

A new predictive equation to calculate resting metabolic rate in athletes.

BACKGROUND: The purposes of the present study were: 1) to examine the accuracy and precision of seven published equations for predicting resting metabolic rate (RMR) in male athletes and 2) to develop a population-specific equation. SETTING: The study occurred during a non-intensive training period. The measurements were performed at the Human Physiology laboratory. PARTICIPANTS: Fifty-one male athletes (22 waterpolo, 12 judo, 17 karate) who exercised regularly at least three hours per day. MEASURES: RMR was measured (mRMR) using indirect calorimetry (ventilated hood system). Besides, mRMR was compared with values predicted (pRMR) using equations of FAO/WHO/UNU, Harris and Benedict, Mifflin et al., Owen et al., Cunningham, Robertson and Reid, Fleisch. Statistical analyses. mRMR was compared with pRMR by means of Student's paired "t" tests, linear regression analysis and the Bland-Altman test. Relationships between mRMR and the different predictive variables were evaluated by Pearson correlation coefficients. The best subset was used to develop the predictive equation for RMR. RESULTS: mRMR was significantly underestimated by six of the seven equations in this sample of athletes. Only the Cunningham equation overestimated (+59 kcal/d) the actual RMR. Bland-Altman 95% limits of agreement were wide (+/- 200-300 kcal/d) for all equations. RMR correlated best with body surface area (r = 0.88), body weight (r = 0.84) and height (r = 0.81). The best-fit equation for the entire data included both weight and height and it was given by: RMR (kcal/d) = -857 + 9.0 (Wt in kg) + 11.7 (Ht in cm) (R2 = 0.78; SEE = 91 kcal/d; 95% IC: -226, 228). CONCLUSIONS: For an individual resting metabolic rate evaluation, the use of indirect calorimetry is recommended. In conditions where this technique cannot be used, our developed equation can predict the RMR of athletes better than any of the currently available prediction equations.

Adult↗

PubMed1998

Solution structure of oxidized rat microsomal cytochrome b5 in the presence of 2 M guanidinium chloride: monitoring the early steps in protein unfolding.

One- and two-dimensional proton NMR spectroscopy has been employed in order to study the denaturation effect of guanidinium chloride (GdmCl) on the oxidized state of the A-form of rat microsomal cytochrome b5 (cyt b5). The protein rapidly starts losing the heme at denaturant concentrations larger than approximately 2.0 M and a largely unfolded protein is eventually obtained. An estimate of the unfolding kinetics is obtained and, by use of a two-state model (folded left and right arrow unfolded), a value for DeltaG degrees. Below this concentration, small (</=0.15 ppm) but systematic chemical shift variations take place for the diamagnetic as well as the hyperfine-shifted signals, indicating that some structural changes occur. However, the protein core maintains its overall structure. The analysis of the two-dimensional nuclear Overhauser effect spectroscopy (2D NOESY) maps has allowed the determination of the solution structure of the protein in the presence of 2 M GdmCl. By use of 1199 meaningful NOESY constraints (obtained from the assignment of 75% of the total protons) and 166 pseudocontact shifts, a family of 40 structures has been obtained through the program PSEUDYANA. The family was further refined through restrained energy minimization and the final root mean square deviation (RMSD) values with respect to the average structure are 0.67 +/- 0.10 A and 1.14 +/- 0.11 A for the backbone and heavy atoms, respectively. The quality of the present structure is equivalent to that of the one obtained recently for the native form [Arnesano et al. (1998) Biochemistry 37, 173-184], thus allowing a meaningful comparison between the two structures. Upon addition of 2 M GdmCl, significant local structural differences are induced to the protein backbone segments comprising residues 33-38 (helix alpha2) and 62-64 (end of helix alpha4-beginning of helix alpha5) while the overall folding scheme of the protein is still maintained. These protein regions form part of the "pocket" supporting the heme, whose plane is also rotated by approximately 10 degrees around an axis connecting the C2 and C8 carbon atoms. The initial steps of the unfolding process involve breaking of a few hydrogen bonds that stabilize local structural conformations. The hydrogen bond between Ser 64 and propionate 7, which stabilizes the heme binding to the protein frame, is broken in the presence of 2 M GdmCl. The same occurs for two hydrogen bonds between two beta-strands (beta2 and beta3), thus inducing the disruption of one of the antiparallel beta-sheets forming one side of the heme cavity. Our results are critically discussed in connection with the native-state protein local backbone mobility characteristics and point to the backbone carbons of Glu 37 and Ser 64 being the first "breaking points" of the protein frame once the global unfolding reaction is initiated at a somewhat higher concentration of denaturant.

Animals↗

PubMed1998

The solution structure of parsley [2Fe-2S]ferredoxin.

The [2Fe-2S]ferredoxin I (Fd I) from parsley leaves (Mr = 10,500; 96 amino acids) in the Fe(III)-Fe(III) oxidized form has been studied by 1H-NMR spectroscopy. Sequence-specific 1H-NMR assignments were obtained through two-dimensional classical double-quantum-filtered-COSY, NOESY and TOCSY spectra. NOEs between protons as close as 5.6 A from the paramagnetic Fe(III) atoms were observed at 800 MHz. A total of 3066 NOEs (of which 2533 are meaningful) and 18 distance constraints taken from X-ray crystallography of the Fe2S2 active site were used to obtain the solution structure. From inversion recovery NOESY experiments, 33 longitudinal relaxation rate (Qpara) constraints were used for the structural refinement. The final structure was obtained by a process of restrained energy minimization. Root-mean-square (rmsd) deviation values obtained for the family of 18 structures (with reference to the average structure) are 0.52 +/- 0.10 A and 0.91 +/- 0.12 A for backbone and all heavy atoms respectively. The structure consists of seven-strands of beta-sheets and four short alpha-helices. The quality of the present solution structure is among the best of those reported for [2Fe-2S]ferredoxins. The secondary structure and overall folding are compared with those of Anabaena variabilis Fd and the higher plant Equistum arvense (horse tail) protein determined through X-ray crystallography. The groups believed to be responsible for electron transfer have been analysed.

Amino Acid Sequence↗

PubMed1998

Solution structure of an artificial Fe8S8 ferredoxin: the D13C variant of Bacillus schlegelii Fe7S8 ferredoxin.

The solution structure of the D13C variant of the thermostable Fe7S8 ferredoxin from Bacillus schlegelii has been determined by 1H-NMR spectroscopy in its oxidized form. In a variable-temperature NMR study the D13C variant was as thermostable (up to 90 degrees C) as the wild-type protein (WT). Seventy-five out of 77 amino acid residues and 81% of all theoretically expected proton resonances in the D13C Fe8S8 protein have been assigned. Its structure was determined through torsion angle dynamics calculations with the program DYANA, using 935 meaningful NOEs (from a total of 1251), hydrogen bond constraints, and NMR-derived dihedral angle constraints for the cluster-ligating cysteines. Afterwards, restrained energy minimization and restrained molecular dynamics were applied to each conformer of the family. The final family of 20 structures has RMSD values from the mean structure of 0.055 nm for the backbone atoms and of 0.099 nm for all heavy atoms. The overall folding of the WT is maintained in the mutant, except for the immediate vicinity of the new cysteine, which becomes much more similar to native Fe8S8 proteins. The two residues at positions 11 and 12, which constitute an insertion with respect to all known Fe8S8 proteins, assume a conformation that does not prevent the preceding and following residues from folding like in native Fe8S8 proteins. Clear evidence for the existence of two conformations involving almost half of the amino acid residues was found. The two conformations are structurally indistinguishable. Temperature-dependent NMR experiments show that one of them is thermodynamically more stable than the other.

Amino Acid Sequence↗

PubMed1998

Probing the backbone dynamics of oxidized and reduced rat microsomal cytochrome b5 via 15N rotating frame NMR relaxation measurements: biological implications.

Rotating frame 15N relaxation NMR experiments have been performed to study the local mobility of the oxidized and reduced forms of rat microsomal cytochrome b5, in the microsecond to millisecond time range. Measurements of rotating frame relaxation rates (R1rho) were performed as a function of the effective magnetic field amplitude by using off-resonance radio frequency irradiation. Detailed analysis of the two data sets resulted in the identification of slow motions along the backbone nitrogens for both oxidation states of the protein. The local mobility of reduced and oxidized cytochrome b5 turned out to be significantly different; 28 backbone nitrogens of the oxidized form were shown to participate in a conformational exchange process, while this number dropped to 12 in the reduced form. The correlation time, tauex, for the exchange processes could be determined for 21 and 9 backbone nitrogens for oxidized and reduced cytochrome b5, respectively, with their values ranging between 70 and 280 microseconds. The direct experimental evidence provided in this study for the larger mobility of the oxidized form of the protein is consistent with the different backbone NH solvent exchangeability recently documented for the two oxidation states [Arnesano, F., et al. (1998) Biochemistry 37, 173-184]. Our experimental observations may have significant biological implications. The differential local mobility between the two oxidation states is proposed to be an important factor controlling the molecular recognition processes in which cytochrome b5 is involved.

Animals↗

PubMed1998

800 MHz 1H NMR solution structure refinement of oxidized cytochrome c7 from Desulfuromonas acetoxidans.

The solution structure of Desulfuromonas acetoxidans cytochrome c7 has been refined by using 1H-NMR spectra recorded at 800 MHz and by using pseudocontact shifts in the final energy minimization procedure. The protein, composed of 68 amino acids, contains three paramagnetic heme moieties, each with one unpaired electron. The largely distributed paramagnetism broadens the lines in several protein parts. The structure is now relatively well resolved all over the backbone by the use of 1315 meaningful NOEs and 90 pseudocontact shifts. The statistical analysis of the structure indicates its satisfactory quality. The protein-fold is quite similar to that of the analogous four-heme cytochromes c3 for those parts which can be considered homologous. The solvent accessibility and the electrostatic potential surfaces surrounding the three hemes have been analyzed in terms of their reduction potentials. The resulting magnetic susceptibility anisotropy data obtained from pseudocontact shifts are analyzed in terms of structural data.

Amino Acid Sequence↗

PubMed1998

Monitoring the conformational flexibility of cytochrome c at low ionic strength by 1H-NMR spectroscopy.

Horse heart cytochrome c at pH 7 and low ionic strength is present as two conformers, as evidenced by 1H-NMR spectroscopy. The two structures have been calculated using NOE and pseudocontact shift constraints. They have the same folding patterns and are essentially equal, within the rmsd of the families. The two average structures have rmsd values of 0.049 nm and 0.093 nm for the backbone and the heavy atoms, respectively. Such a difference has been analyzed through a detailed analysis of the NOEs. It appears that the species at low ionic strength differs from the species present at high ionic strength by the displacement of some external residues, such as Gln16, Ile81 and Glu90. Other changes are monitored by the chemical shifts but they cannot be quantified at the present level of resolution. Ionic-strength-dependent structural rearrangements may be relevant with respect to the problem of molecular recognition.

Algorithms↗

PubMed1998

Solution structure of reduced monomeric Q133M2 copper, zinc superoxide dismutase (SOD). Why is SOD a dimeric enzyme?.

Copper, zinc superoxide dismutase is a dimeric enzyme, and it has been shown that no cooperativity between the two subunits of the dimer is operative. The substitution of two hydrophobic residues, Phe 50 and Gly 51, with two Glu's at the interface region has disrupted the quaternary structure of the protein, thus producing a soluble monomeric form. However, this monomeric form was found to have an activity lower than that of the native dimeric species (10%). To answer the fundamental question of the role of the quaternary structure in the catalytic process of superoxide dismutase, we have determined the solution structure of the reduced monomeric mutant through NMR spectroscopy. Another fundamental issue with respect to the enzymatic mechanism is the coordination of reduced copper, which is the active center. The three-dimensional solution structure of this 153-residue monomeric form of SOD (16 kDa) has been determined using distance and dihedral angle constraints obtained from 13C, 15N triple-resonance NMR experiments. The solution structure is represented by a family of 36 structures, with a backbone rmsd of 0.81 +/- 0.13 A over residues 3-150 and of 0.56 +/- 0.08 A over residues 3-49 and 70-150. This structure has been compared with the available X-ray structures of reduced SODs as well as with the oxidized form of human and bovine isoenzymes. The structure contains the classical eight-stranded Greek key beta-barrel. In general, the backbone and the metal sites are not affected much by the monomerization, except in the region involved in the subunit-subunit interface in the dimeric protein, where a large disorder is present. Significative changes are observed in the conformation of the electrostatic loop, which forms one side of the active site channel and which is fundamental in determining the optimal electrostatic potential for driving the superoxide anions to the copper site which is the rate-limiting step of the enymatic reaction under nonsaturating conditions. In the present monomer, its conformation is less favorable for the diffusion of the substrate to the reaction site. The structure of the copper center is well-defined; copper(I) is coordinated to three histidines, at variance with copper(II) which is bound to four histidines. The hydrogen atom which binds the histidine nitrogen detached from copper(I) is structurally identified.

Amino Acid Substitution↗

PubMed1998

Solution structure of the oxidized Fe7S8 ferredoxin from the thermophilic bacterium Bacillus schlegelii by 1H NMR spectroscopy.

The solution structure of the paramagnetic seven-iron ferredoxin from Bacillus schlegelii in its oxidized form has been determined by 1H NMR. The protein, which contains 77 amino acids, is thermostable. Seventy-two residues and 79% of all theoretically expected proton resonances have been assigned. The structure has been determined through torsion angle dynamics calculations with the program DYANA, using 966 meaningful NOEs (from a total of 1305), hydrogen bond constraints, and NMR derived dihedral angle constraints for the cluster ligating cysteines, and by using crystallographic information to build up the two clusters. Afterwards, restrained energy minimization and restrained molecular dynamics were applied to each conformer of the family. The final family of 20 structures has RMSD values from the mean structure of 0.68 A for the backbone atoms and of 1.16 A for all heavy atoms. The contributions to the thermal stability of the B. schlegelii ferredoxin are discussed by comparing the present structure to that of the less stable Azotobacter vinelandii ferredoxin I which is the only other available structure of a bacterial seven-iron ferredoxin. It is proposed that the hydrophobic interactions and the hydrogen bond network linking the N-terminus and the C-terminus together and a high number of salt bridges contribute to the stability.

Amino Acid Sequence↗

PubMed1998

Monitoring the role of oxalate in manganese peroxidase.

The water proton relaxation rate measurements between 0.01 and 50 MHz on water solutions containing the cyanide adduct of the manganese-depleted manganese peroxidase (MnP-CN-) and increasing amounts of Mn2+ have been determined. The proton relaxivity curves have shown evidence of the formation of the protein/Mn2+ complex and have been analyzed in order to obtain spin Hamiltonian parameters and correlation times. Oxalate is shown not to alter the above profiles. This suggests that no protein-Mn2+-oxalate ternary complex is formed and that oxalate does not remove Mn2+ from the protein. On the basis of high-resolution 1H NMR experiments, we propose that Ce3+ and Gd3+ bind at the manganese site, and, on the basis of the charge, we propose that they may mimic Mn3+. The water proton relaxation rates of water solutions containing manganese-depleted MnP-CN- and increasing amounts of Gd3+ have been measured and analyzed. Oxalate is shown to remove the trivalent metal ions. This suggests that trivalent metal ions bind oxalate and diffuse away from the protein presumably as oxalate complexes. Implications for the enzymatic mechanism are discussed.

Binding Sites↗

PubMed1998

Solution structure of oxidized cytochrome c6 from the green alga Monoraphidium braunii.

Cytochrome c6 from Monoraphidium braunii, an 89-amino acid electron transfer protein, has been investigated by NMR in solution, in its oxidized form, at pH 7 and 300 K. By using a combination of COSY, TOCSY, and NOESY experiments, 84% of the proton resonances have been assigned. A total of 1668 experimental NOE constraints, 1109 of which were meaningful, together with 288 pseudocontact shifts, have been used to determine the structure in solution. This is represented as a family of 40 structures which have been energy minimized. The rmsd values with respect to the mean structure are 0.57 +/- 0.08 and 0.94 +/- 0.09 A for the backbone and heavy atoms, respectively. The structure has been found to be very similar to that of the reduced form, except for a rearrangement in propionate 7, a feature which has been observed in all c-type cytochromes investigated so far. Such a feature could be relevant for the efficiency of the electron transfer pathway with either the oxidizing or the reducing partners. Other differences in the oxidation states have been noted in the region proposed to be involved in the interaction with the physiological partners.

Amino Acid Sequence↗

PubMed1998

The solution structure of oxidized rat microsomal cytochrome b5.

The solution structure of oxidized rat microsomal cytochrome b5 has been obtained from 1H NMR spectra measured at 800 MHz. The available assignment has been extended to 78% of the total protons and 95% of the residues. From 1372 meaningful NOEs, a family of 40 structures has been obtained through the program DYANA; 235 pseudocontact shifts have been then added as further constraints, obtaining an essentially similar family of structures. This latter family has been further refined through restrained energy minimization. The final RMSD values with respect to the average structure are 0.58 +/- 0.10 A and 1.05 +/- 0.11 A for backbone and heavy atoms, respectively. The high quality of the structure allows meaningful comparisons with the solution structure of the reduced protein, with the X-ray and solution structures of the oxidized bovine isoenzyme, and with the solution structure of the apoprotein. Upon loss of one electron, the heme plane undergoes a change in its orientation, possibly due to the change of the total charge. Propionate 7 appears to have a conformation which is dependent on the oxidation state of the iron. Helices alpha2 and alpha4 also experience changes in their average positions in the two oxidation states. Finally, the backbone NHs experience different exchange properties in the two oxidation states. While those present in the beta sheets forming the basis of the heme pocket are nonexchanging in both oxidation states, the NHs in the helices forming the heme-binding pocket are exchanging with the bulk solvent in the oxidized form, indicating larger local mobility in this state. This observation could suggest that, to optimize the electron transfer process, the local mobility should be properly tuned.

Amino Acid Sequence↗