Electron-transfer-mediated binding of optically active cobalt(III) complexes to horse heart cytochrome c.
Optically active cobalt(II) complexes are used as reducing agents in the electron-transfer reaction involving horse heart cytochrome c. Analysis of the circular dichroism (CD) spectra of reaction products indicates that the corresponding cobalt(III) species of both enantiomers of [CoII(alamp)] (H2alamp=N,N'-[(pyridine-2,6-diyl)bis(methylene)]-bis[alanine]) are partly attached to the protein during electron transfer by coordination to an imidazole unit of one of the histidine residues. His-26 and His-33 are both solvent exposed, and the results suggest that one of these histidine residues acts as a bridge in the electron transfer to and from the haem iron of cytochrome c. The reaction is enantioselective: the ratio of the relative reactivity at 15 degrees C is 2.9 in favour of the R,R-enantiomer. A small induced CD activity in the haem chromophore reveals that some structural changes in the protein occur consecutively with the binding of the cobalt(III) complex.
Scholten
Ulrich
U
Institut de Chimie, Université de Neuchâtel, Rue Emile-Argand 11, Case postale 2007, Neuchâtel, Switzerland.
Merchán
Alejandro Castillejo
AC
Bernauer
Klaus
K
D000818:Animals; D002942:Circular Dichroism; D003035:Cobalt / Q000737:chemistry* / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism*; D004579:Electron Transport; D006736:Horses; D009206:Myocardium; D011485:Protein Binding
D003035:Cobalt; D045304:Cytochromes c