Figure 11. Sequence alignment of cytochromes c₁ with other class I cytochromes. The alignment of cytochromes c1 (1BCC), c (1HRC, 1YCC), c₂ (1C2R), c₆ (1CYI), and c₈ (351C) are based on superimposed structures from the indicated PDB entries. The other cytochromes c₁ for which no structure is available were aligned by conventional sequence alignment. Boxed regions of the sequence indicate the 3 conserved helices 1, 3, and 5; helices 2 and 4 in cytochromes c and c₂; helix 2' in cytochrome c₁; and the heme-bracing PXL tripeptide. Highly conserved residues are indicated in bold type. The sequence numbering of horse cytochrome c is indicated at the top, and that for bovine cytochrome c₁ at the bottom.