Fig. 1.

Catalytic core of cytochrome bc₁. (A) H-shaped electron transfer system formed by cofactor chains of: cytochrome b (blue), cytochrome c₁ (purple) and FeS subunits (green). Electron entry sites (double arrow), electron paths (dotted lines). (B) Crystal structure of R. capsulatus cytochrome bc₁ dimer (PDB: 1ZRT). Heme and FeS cofactors are blue. Cytochrome b subunit of one monomer is shown in red and depicts those amino acids that are different in R. sphaeroides (green sticks) to illustrate the heterogeneity of hybrid fusion protein used in this study.