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: 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.