Fig. 5. The selected mutations in Serinus are concentrated on the matrix side of cytochrome b in the vicinity of the ubiquinone binding site Q_i. Sixteen complete or nearly complete cytochrome b sequences of species of the oscine genus Serinus were aligned and used to derive a consensus sequence, which was aligned with the sequence of the non-oscine genus Empidonex. The location of the substitutions was mapped onto the chicken cytochrome b structure (3BCC) (Zhang et al., 1998), which is shown as a three-dimensional model. The location of a conserved substitution is indicated by a blue ball on the protein backbone, and that of a non-conserved substitution is indicated by a red ball. The top of the structure faces the mitochondrial matrix and includes the Q_i ubiquinone binding site (with bound ubiquinone) and the b_H heme (blue). The bottom of the structure faces the intermembrane space and includes the Q_o ubiquinone binding site (with bound Stigmatellin) and the b_L heme (magenta).