MXD3 is a member of the Myc superfamily of basic helix-loop-helix leucine zipper transcriptional regulators. The protein forms a heterodimer with the cofactor MAX which binds specific E-box DNA motifs in the promoters of target genes and regulates their transcription. Disruption of the MAX-MXD3 complex is associated with uncontrolled cell proliferation and tumorigenesis. Transcript variants of this gene encoding different isoforms have been described. Recombinant human MXD3 protein, fused to His-tag at N-terminus, was expressed in E.coli.