Fig. 2.

Conservation of ABCG5 and ABCG8 polypeptide sequences in the animal kingdom. Polypeptide sequences for man, chimpanzee, dog, cow, rat, mouse, chicken, toad, and two fishes, Zebra fish and Fugu, were compiled from the publicly available databases. Panel a shows the homology for ABCG5 and panel b that for ABCG8. Homologies around the nonsynonymous changes in humans are shown. It should be noted that the sequences for all but man, mouse, and rat are considered preliminary and need to be parsed for accuracy. For example, the exact start translation sites for some of these have not been established and in some cases, the protein translation is based upon electronically predicted exons, which seem to be incorrect. Despite these reservations, mapping the nonsynonymous changes seen at the STSL locus in humans onto these homology comparisons shows that many of these polymorphisms affect highly conserved residues. It is therefore remarkable that these ‘polymorphisms’ are not ‘disease’-causing (see text for discussion). Note that the variable amino acids not conserved in fish and chicken may turn out to be conserved once the genome sequences for these organisms have been ‘cleaned up’. A complete homology comparison for both genes is available on request from the authors