Multiple sequence alignment of b5-domains. This figure has been generated using the Jalview program written by Michele Clamp. Proteins are described by their SWISS-PROT identifier or accession number/start-end, and the class they belong to is indicated on the right. Alignments are colored using the ClustalX scheme in Jalview (orange, glycine (G); light green, proline (P); blue, small and hydrophobic amino acids (A, V, L, I, M, F, W in single-letter amino acid code); dark green, hydroxyl and amine amino acids (S, T, N, Q); magenta, negatively charged amino acids (D, E); red, positively charged amino acids (R, K); dark-blue, histidine (H) and tyrosine (Y). The top line indicates secondary structural elements obtained from bovine microsomal cytochrome b5 (PDB 1cyo): magenta rectangles represent α helices, and yellow arrows represent β strands. The two positions marked 'H' indicate the conserved pair of heme-coordinating histidines in the heme-binding b5-domains. The numbers in square brackets indicate the numbers of residues not shown in this illustration.