Maf family members form a unique subclass of basic-leucine zipper (bZIP) transcription factors. Maf proteins are subdivided into two groupings: large, including c-Maf, Nrl, MafA, and MafB; and small, including MafF, MafG, and MafK. Large Mafs contain an N-terminal acidic domain important for transcriptional activation that is lacking in small Maf family members.
MafB has been implicated in the regulation of hindbrain development. Heterodimers of MafK and p45 NF-E2, another bZIP factor, promote globin gene expression and erythroid differentiation in erythroleukemia cells. Small Maf/Nrf2 heterodimers have been shown to be involved in the regulation of antioxidant response element-dependent genes.