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

The EPR spectral parameters of aa(3) oxidase and cyt c(552) from Paracoccus denitrificans were studied in purified oxidase and enriched cyt c(552). The orientation of the g-tensors of hemes a and c(552) were determined on partially ordered membranes, enriched cyt c(552) and a c(552):aa(3) subcomplex. The known correlation of g-tensor to molecular axes in histidine/methionine ligated hemes permits us to position cyt c(552) with respect to the parent membrane. Taken together with previous data on the interaction surface between aa(3) oxidase and cyt c(552), these results allow us to arrive at a single conformation for the c(552):aa(3) electron transfer complex.