Conformational studies cytochrome

We have already noted that extensive conformational studies suggest that the metal substituted cytochromes c (eg Zncytc, porphcytc) are essentially isostructural with Fecytc. Thus we expect that for the Zn, Fe, and H. porphyrin cyto chromes metal-porphyrin dependent variations in structure will not greatly affect the general trend observed for the dependence of rate on AG. 

Molecular hysteresis could be possible in metalloproteins. Barker et al. [32] studied cytochrome c in which oxidation state was linked with conformational... 

ZhouJ, ZhengJ, Jiang SY Molecular simulation studies of the orientation and conformation of cytochrome c adsorbed on self-assembled monolayers, J Phys Chem B 108 17418-17424, 2004b. 

For the cytochrome c-plastocyanin complex, the kinetic effects of cross-linking are much more drastic while the rate of the intracomplex transfer is equal to 1000 s in the noncovalent complex where the iron-to-copper distance is expected to be about 18 A, it is estimated to be lower than 0.2 s in the corresponding covalent complex [155]. This result is all the more remarkable in that the spectroscopic and thermodynamic properties of the two redox centers appear weakly affected by the cross-linking process, and suggests that an essential segment of the electron transfer path has been lost in the covalent complex. Another system in which such conformational effects could be studied is the physiological complex between tetraheme cytochrome and ferredoxin I from Desulfovibrio desulfuricans Norway the spectral and redox properties of the hemes and of the iron-sulfur cluster are found essentially identical in the covalent and noncovalent complexes and an intracomplex transfer, whose rate has not yet been measured, takes place in the covalent species [156]. 

Heimburg, T, HUdebrandt, P., and Marsh, D., 1991, Cytochrome c-hpid interactions studied by resonance Raman and P NMR spectroscopy. Correlation between the conformational changes of the protein and the lipid bUayer Biochemistry 30 9084-9089. 

Several studies have dealt with the influence of lipids on conformational equilibria in cytochrome c via hydrophobic and electrostatic interactions. The binding of sodium dodecyl sulfate monomers and micelles was reported to cause a transition of cytochrome c to a state B2 which is of potential physiological relevance. The interplay between heme only state changes and secondary structure changes was analyzed by freeze-quench and stopped-flow experiments.276 The response of the heme spin state to lipid acyl chains in cytochrome c was... 

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