Figure 4

Phylogenetic tree of ABCB proteins in four eukaryote genomes. A phylogeny derived and displayed according to the procedure outlined in the legend to Figure 3. Shown here is the division between the half transporters, which are most of the ABCB genes in mammals, and the full-transporters (called P-glycoproteins (P-gps)) that have evolved from them. Four lineages of P-gps (exemplified by genes F22E10.1-4, T21E8.1-3, C47A10.1 and C54D1.1) have been lost in both flies and mammals, and of the two remaining P-gp lineages, one has been lost in each of the fly and human lines of descent. Subsequent duplications within the single remaining P-gp lineage in both flies and mammals have not been sufficient to keep pace with continuing P-gp duplications in the worm genome.