Basic leucine zipper domains (bZIP) are important recognition sequences found in transcription factors. These coiled-coil dimers have specific resides at the end, allowing the recognition of a defined DNA sequence. Due to every seventh reside being a leucine, these protein domains have a hydrophobic side. This amphipathicity allows the protein to dimerise, forming the zipper domain.
bZIP domains can be combined with other DNA-binding domains, such as zinc-finger proteins and homeodomain folds. This increases the number of nucleotides in the recognition sequence, increasing the specificity.