Transcription regulator. Forms a sequence-specific DNA-binding protein complex with MYC or MAD which recognizes the core sequence 5'-CAC[GA]TG-3'. The MYC-MAX complex is a transcriptional activator, whereas the MAD-MAX complex is a repressor. Efficient DNA binding requires dimerization with another bHLH protein. Binds DNA as a heterodimer with MYC or MAD. Embryo, especially in central nervous system. Highest expression in embryos. Belongs to the MAX family. Intron retention.