Transcriptional activator that binds to the G-box motif (5'-CACGTG-3') and other cis-acting elements with 5'-ACGT-3' core, such as Hex, C-box and as-1 motifs. Possesses high binding affinity to G-box, much lower affinity to Hex and C-box, and little affinity to as-1 element (PubMed:18315949). G-box and G-box-like motifs are cis-acting elements defined in promoters of certain plant genes which are regulated by such diverse stimuli as light-induction or hormone control (Probable). Binds to the G-box motif 5'-CACGTG-3' of LHCB2.4 (At3g27690) promoter. May act as transcriptional repressor in light-regulated expression of LHCB2.4. Binds DNA as monomer. DNA-binding activity is redox-dependent (PubMed:22718771). Monomer, homodimer and heterodimers with BZIP68 and GBF1/BZIP41 (PubMed:18315949, PubMed:22718771). Heterodimers with GBF2/BZIP54 and GBF3/BZIP55 (PubMed:18315949). Binds DNA as monomer and forms homo- and heterodimers. The monomeric form is redox regulated (PubMed:22718771). Interacts with GIP1 (PubMed:25387999). The N-terminal region is necessary for its transcriptional activity. Belongs to the bZIP family.