Fig. 2

Evolutionary conservation of HAP1_N and Milt/TRAK domains. A common ancestor to TRAK-like proteins is predicted to exist prior to the divergence of protostomes and deuterostomes containing a HAP1_N domain (red) and Milt/TRAK domain (purple). In protostomes, the Milt/TRAK domain has been lost from the single homolog in C. elegans (T27A3.1), but has been maintained in Drosophila Milton. In vertebrates, gene duplication has given rise to 3 paralogous genes encoding HAP1, TRAK1 and TRAK2, prior to the divergence of the 5 classes of vertebrate. In non-eutherian vertebrates, HAP1 is a TRAK-like protein with a HAP1_N and Milt/TRAK domain. The TRAK domain has subsequently been lost in the divergence of eutherian mammals