Topography of tyrosine residues and their involvement in peroxidation of polyunsaturated cardiolipin in cytochrome c/cardiolipin peroxidase complexes

► Cyt c forms complexes with cardiolipin (CL) and catalyzes CL peroxidation. ► Tyrosyl radicals are reactive intermediates of cyt c/CL peroxidase. ► Tyr67 is closest to the heme-iron of cyt c. ► Tyr67 mutant displayed weakest EPR radical signals and lowest CL peroxidation. ► Tyr67 is a likely electron-donor in the oxygenase half-reaction of cyt c/CL complex.