It is a common feature that most bZIP
Walrycin B factors can form homodimer. Few examples were reported which bZIPs are capable of forming only heterodimers, such as the Fos protein from mammals and the Arabidopsis AtGBF4 protein. In the leucine zipper region of the Fos protein, 5 of 8 e and g positions, which are important to dimmer formation, are occupied by glutamate residues and no basic residue present, the inability of the Fos protein to homodimerize is due to electrostatic destabilization of the protein–protein interaction by these acidic residues. They mediate gene
expression by forming heterodimers with various Jun proteins, these heterodimers are more stable than the Jun–Jun dimers and possess higher DNA binding activity [11], [23] and [24]. Similar situation is observed in AtGBF4, the leucine zipper region of AtGBF4 contains predominately glutamate residues at the e and g positions, which hinders the formation of homodimers, but AtGBF4 forms heterodimers with GBF2, 3 and bind G-box [14].
