Application of exciton coupling theory to the structure of mitochondrial cytochrome b.
The circular dichroism of the reduced bis-heme mitochondrial cytochrome b in the Soret region has been analyzed using exciton theory. The theory was applied to a geometric model that reflects the current consensus of the structure of this membrane protein [Degli Esposti, M., De Vries, S., Crimi, M., Ghelli, A., Patarnello, T., & Meyer, A. (1993) Biochim. Biophys. Acta 1143, 243-271]. The analysis suggests that the iron-iron distance is about 19.5 A, with a possible range of 17-23 A; the two hemes appear to be canted at 45 degrees with respect to one another. It appears that the two hemes undergo a relative angular displacement upon reduction, suggesting some flexibility in the protein structure. Some applications of this analysis to other bis-heme proteins are considered.
Palmer
G
G
Department of Biochemistry & Cell Biology, Rice University, Houston, Texas 77251-1892.
Degli Esposti
M
M
D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D003573:Cytochrome b Group / Q000737:chemistry* / Q000302:isolation & purification; D014450:Electron Transport Complex III / Q000737:chemistry / Q000302:isolation & purification; D008433:Mathematics; D008929:Mitochondria, Heart / Q000378:metabolism; D008961:Models, Structural; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013053:Spectrophotometry
D003573:Cytochrome b Group; D014450:Electron Transport Complex III