leucine zipper found in the TSC22 domain leucine zipper transcription factors, c-Myc-binding protein, and similar proteinsThe family includes TGF-beta-stimulated clone-22 domain (TSC22D) leucine zipper transcription factors, TSC22D1-4, as well as c-Myc-binding protein (MycBP). TSC22D proteins have diverse physiological functions, including cell growth, development, homeostasis, and immune regulation. MycBP, also called associate of Myc 1 (AMY-1), is a novel c-Myc binding protein that may control the transcriptional activity of Myc. It stimulates the activation of E box-dependent transcription by Myc. Members of this family contain a conserved leucine zipper (ZIP) domain. Its first helix is not basic and does not contain the consensus sequence, NXX(A)(A)XX(C/S)R, found in most basic region/leucine zipper (bZIP) proteins. In the bZIP family of transcription factors, the leucine zipper acts as a dimerization domain and the upstream basic region as a DNA-binding domain. However, DNA-binding capability of TSC22D family proteins is not obvious, due to the lack of the basic region found in the original bZIP DNA-binding domains. Similar to bZIP, ZIP forms homo- and heterodimers, resulting in many dimers that may have different effects on transcription.