TMSs 1–3 compared with TMSs 4–6 of an ABC type 2 ancestral sequence. The comparison score was 39.9 SD with 58.5% similarity and 50.4% identity. The numbers at the beginning of each line refer to the residue numbers in each of the proteins. TMSs are indicated in red lettering. Vertical lines indicate identities; colons indicate close similarities, and periods indicate more distant similarities.