FIG. 3.

(A) Tree of the ABCA family. The complete amino acid sequences of the ABCA transporters were aligned and related to each other and homologs from other species. In this and other figures, the bootstrap values are presented for unrooted trees. Full transporters with two TM-ABC domains formed a single group that clustered with homologs in Trypanosoma cruzi (Tc), Homo sapiens (Hs), and A. thaliana (At). Two half-transporters clustered with other genes from these organisms as well as one from E. histolytica (Eh). Sequences of genes shown in this and other figures are available on the website (http://www.biology.ucsd.edu/labs/loomis/ABCwebsite/abcfamily.html).(B) Proposed order of gene loss in the ABCA family. The common ancestor of animals, plants, fungi, and Dictyostelium is presumed to have carried a gene encoding a half-transporter as well as one encoding a full transporter. The half-transporter was lost in the line leading to animals and fungi before these two kingdoms diverged. The full transporter was subsequently lost from the progenitor of fungi. Gene losses are indicated by an X.