The newly emerged Maf family proteins possess a highly conserved basic leucine zipper (bZip) domain in common and are subdivided into large and small Maf proteins. The Maf family proteins appear to regulate cell differentiation processes and also cellular functions as partner molecules of CNC family proteins. Organization of the small maf genes are highly conserved in vertebrates, suggesting an important functional contribution of the gene products. Human MAFG and MAFK are located at 17q25 and 7p22, respectively. Thus, small maf genes are not clustered in a single locus.