Differences in the solution structures of oxidized and reduced cytochrome c measured by small-angle x-ray scattering

While X-ray crystallographic data on cytochrome c show the reduced and oxidized forms to have very similar structures, there is a considerable body of data, mostly from solution studies, that indicates the reduced form is more stable and that the interior of the protein is less accessible to solvent...

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Bibliographic Details
Published in:	Biochemistry (Easton) Vol. 27; no. 4; pp. 1121 - 1125
Main Authors:	Trewhella, Jill, Carlson, Vanice A. P, Curtis, Elizabeth H, Heidorn, Douglas B
Format:	Journal Article
Language:	English
Published:	Washington, DC American Chemical Society 23-02-1988
Subjects:	Biological and medical sciences cytochrome c Cytochrome c Group - metabolism Fundamental and applied biological sciences. Psychology Kinetics Molecular biophysics Oxidation-Reduction Physico-chemical properties of biomolecules Protein Conformation Solutions X-Ray Diffraction - methods X-ray scattering Heart Redox state Molecular form Hemoprotein Radius of gyration Small angle X ray scattering Cytochrome c Vertebrata Mammalia Horse Perissodactyla Ungulata Solution
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Summary:	While X-ray crystallographic data on cytochrome c show the reduced and oxidized forms to have very similar structures, there is a considerable body of data, mostly from solution studies, that indicates the reduced form is more stable and that the interior of the protein is less accessible to solvent in this state. These observations have led to the hypothesis that while the time-averaged structure is preserved between the two forms, the dynamics of the two forms are different. The oxidized form has been proposed to undergo more large-amplitude, low-frequency motions than the reduced form. The crystal structure data were derived from crystals grown in high salt concentrations, but the solution studies were done at relatively low ionic strength. Small-angle X-ray scattering has been used to examine the effects of the ionic strength and oxidation state on the solution structure of cytochrome c. We find that the radius of gyration and the maximum linear dimension of oxidized cytochrome c are significantly larger than those for reduced cytochrome c, in 5 mM phosphate buffer at pH 7.3, and further that this difference is suppressed by addition of 200 mM sodium chloride. We conclude that there is a real structural difference between the two forms at low ionic strength in solution and that this difference is likely to contribute to the observed differences in accessibility and compressibility.
Bibliography:	ark:/67375/TPS-GZLDH8TB-C istex:C1BA84EE66BC328499F176BD1AAFD2D8DBAEFCAD ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0006-2960 1520-4995
DOI:	10.1021/bi00404a007