Kinetic studies on a cross-linked complex between plastocyanin cytochrome f.
A cross-linked complex between plastocyanin and cytochrome f was prepared by incubation in the presence of a water soluble carbodiimide and its kinetic properties were studied. The optical spectra, oxidation-reduction potentials and isoelectric pH of plastocyanin and cytochrome f did not change upon the formation of the cross-linked complex. Studies on the ionic strength effect on the electron transfer rate from cross-linked plastocyanin to ferricyanide indicated that the negative charge on the reaction site of plastocyanin was masked upon the cross-linking. It was also suggested that the sign of the net charge near the cytochrome f heme edge changed from positive to negative upon the cross-linking. On the other hand, electrostatic interactions between cross-linked plastocyanin and P700 seemed to be essentially the same as those in the case of native plastocyanin, although the rate of electron transfer from cross-linked plastocyanin to P700 was severely reduced. We also measured the intra-complex electron transfer from cytochrome f to plastocyanin. This suggested that the covalently cross-linked complex is a valid model of the electron transfer encounter complex. Based on these results, the reaction sites of plastocyanin with P700 and cytochrome f were discussed.
Takabe
T
T
Department of Chemistry, Faculty of Science and Technology, Meijo University, Aichi.
Ishikawa
H
H
D002234:Carbodiimides; D002851:Chromatography, High Pressure Liquid; D003580:Cytochromes / Q000378:metabolism*; D045348:Cytochromes f; D004591:Electrophoresis, Polyacrylamide Gel; D007525:Isoelectric Focusing; D007700:Kinetics; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000378:metabolism*; D010944:Plants; D010970:Plastocyanin / Q000378:metabolism*
D002234:Carbodiimides; D003580:Cytochromes; D010940:Plant Proteins; D010970:Plastocyanin; D045348:Cytochromes f