The orientation of a heme of cytochrome c oxidase in submitochondrial particles.

The electron paramagnetic resonance of the low spin signal from oxidized cytochrome c oxidase has been studied in oreinted multilayers of submitochondrial and electron transport particles. Measurements of the angular variation of the EPR spectra with the multilayer plane orientation allow the determination of the heme orientation in the multilayer. The heme normal lies in the membrane plane and the y-axis of the heme makes an angle of 30 degrees with the membrane normal. Analysis of the line shape reveals the presence of mosaic spread in the multilayer almost half of which is attributable to deviations of protein orientation within the membrane.