Figure 3.

The APB Motif.

(A) Alignments of the predicted N-terminal (1 to 100) amino acid sequences of 12 members of the AtbHLH subfamily 15 containing amino acid sequence homologies to the APB motif. Conserved amino acid sequences (in red) of the APB motif (blue outlined) are shown. The invariant amino acid residues required for APB function (reverse red font) are E31, L32, G37, and Q38 (PIF3 and PIF5 positions). The APB consensus is in bold type.

(B) Phylogenetic neighbor-joining tree of the aligned APB sequences showing the putative evolutionary relationships of the APB motif between the family members. The distance values (changes) between sequences are proportional to the branch lengths (indicated). Proteins that interact with phyB (Pfr) are in red, and those that were tested but do not interact are in blue. The APB region of BHLH023 has a variation (S35 instead of invariant G).