Conformation of the c₅₅₂:aa₃ electron transfer complex in Paracoccus denitrificans studied by EPR on oriented samples

The EPR spectral parameters of aa₃ oxidase and cyt c₅₅₂ from Paracoccus denitrificans were studied in purified oxidase and enriched cyt c₅₅₂. The orientation of the g-tensors of hemes a and c₅₅₂ were determined on partially ordered membranes, enriched cyt c₅₅₂ and a c₅₅₂:aa₃ subcomplex. The known correlation of g-tensor to molecular axes in histidine/methionine ligated hemes permits us to position cyt c₅₅₂ with respect to the parent membrane. Taken together with previous data on the interaction surface between aa₃ oxidase and cyt c₅₅₂, these results allow us to arrive at a single conformation for the c₅₅₂:aa₃ electron transfer complex.