Artificial electron transport mediated by trinitrophenyl groups introduced into protein molecules by means of chemical modification.

Spinach ferredoxin was found to lose its iron-sulfur center during trinitrophenylation. The loss of the iron-sulfur center resulted in disappearance of its activities as electron mediators in the NADP+ photoreduction and NADPH-cytochrome c reduction systems, whereas it did not affect the activity in the cytochrome c photoreduction system. Based on the experimental evidence that ovalbumin, originally inactive in electron transport, became active in the cytochrome c photoreduction system after trinitrophenylation, the retained activity of the modified ferredoxin was concluded to be due not to the original function of the iron-sulfur center, but to artificial electron transport mediated by TNP groups introduced into the protein molecule. Trinitrophenylated cytochrome c was also active as a mediator, but lost its ability as a terminal acceptor in the system.