B3 domain

The B3 DNA binding domain (DBD) is a highly conserved domain found exclusively in transcription factors (≥40 species) combined with other domains. It consists of 100-120 residues, includes seven beta strands and two alpha helices that form a DNA-binding pseudobarrel protein fold ; it interacts with the major groove of DNA.

B3 families
In Arabidopsis thaliana, there are three main families of transcription factors that contain B3 domain:
 * ARF (Auxin Response Factors)
 * ABI3 (ABscisic acid Insensitive3)
 * RAV (Related to ABI3/VP1)

and are only known NMR solution phase structures of the B3 DNA Binding Domain.

Related proteins
The N-terminal domain of restriction endonuclease EcoRII; the C-terminal domain of restriction endonuclease BfiI possess a similar DNA-binding pseudobarrel protein fold.