Structure of the R2R3 domain of different MYB proteins. (A) Protein sequence alignment of the R2R3 domain of grapevine MYB transcription factors regulating the flavonoid pathway and mouse (Mus musculus) c-MYB. GenBank accession numbers are indicated below: VvMYB5b (AY899404), VvMYB5a (AY555190), VvMYBPA1 (AM259485), VvMYBA1 (AB097923), and Mmc-MYB (NP_034978). Identical residues are shown in white on a red background, and conserved residues are red. The R/L mutation is indicated with a dark triangle, residues interacting with DNA bases [30, 35] are indicated with either a dark square or an asterisk for strong and weak interactions respectively. Dark circles denote residues interacting with bHLH partners . Diamonds denote residues involved in the hydrophobic pocket in domain R2 and amino acids involved in salt bridge interactions in Mmc-MYB  are highlighted with red arrow heads. This figure was drawn using web ESPript . (B) R2 and R3 domains of the VvMyb5b modeled structure obtained deduced from the X-ray diffraction structure of the mouse c-MYB proto-oncogene R2-R3 domain (pdb entry code 1gv2). The figure was drawn with PyMOL . (C) Stereo view of the environment of residue R69 within the R2 domain.