The transmembrane helices of beef heart cytochrome oxidase.

The locations of the transmembrane helices in the twelve subunits of beef heart cytochrome oxidase were predicted with a modified form of the von Heljne-Blomberg-hydrophobicity scale. Based on about 20 residues per transmembrane helix at most 480 of the estimated 660 helical residues (36.8% of 1793 residues total) are expected to be in transmembrane helices which have their axes in the plane of the membrane. If all other helical residues have their helix axes in the plane of the membrane, the average helical tilt is calculated to be 32 degrees obtained from the ir linear chroism of cytochrome oxidase multilamellar films [M.D. Bazzi & R.W. Woody (December 1985) Biophys. J. 48: 957-966].