– Since they lack a putative transactivation domain, the small Mafs behave as transcriptional repressors when they dimerize among themselves. However, they act as transcriptional activators by dimerizing with other (usually larger) basic-zipper proteins, such as NFE2, NFE2L1/NRF1, NFE2L2/NRF2 and NFE2L3/NRF3, and recruiting them to specific DNA-binding sites. Small Maf proteins heterodimerize with Fos and may act as competitive repressors of the NF-E2 transcription factor. MAFK Protein, Mouse, Recombinant (His & Myc & SUMO) is expressed in E. coli expression system with N-10xHis-SUMO and C-Myc tag. The predicted molecular weight is 37.5 kDa and the accession number is Q61827.