FIG. 2.

Dys belongs to a distinct subfamily of bHLH-PAS proteins. Representatives of all families of bHLH-PAS proteins were compared by using the bHLH domain protein sequences and aligned by using CLUSTALX. The alignment is represented by a phylogram generated by using the neighbor-joining method. The tree demonstrates that DroDys, AnoDys, CeC15C8.2, and H-NXF (HumNXF) represent a distinct, evolutionarily conserved subfamily of bHLH-PAS proteins (bracket). The scale represents the fraction of nonidentical amino acids residues along each branch. Numbers along each branch are the bootstrap confidence limits with 1,000 repetitions. The identities of the other proteins can be found in Taylor and Zhulin (47). The species designation precedes each protein acronym (Ano, A. gambiae; Ce, C. elegans; Dro, Drosophila; Mur, murine; Hum, human).