BZIP proteins dimerization

Fig. 5. (a) A bZIP protein dimer showing the leucine zipper dimerization domain and the two basic domains (b) folded structure of a bZIP protein showing the basic domains binding in the major groove of the target DNA. Reprinted from A. Travers, DNA-Protein Interactions, Chapman Hall, 1993. With permission from A. Travers. 

Calculations. It has not been established whether all bZIP proteins bind DNA as pre-assembled dimers in a single step or whether two protein monomers bind sequentially with dimerization occurring on the DNA. If dimerization precedes DNA binding, the binding reaction will be described by scheme 1 ... 

As mentioned above, the bZIP proteins function as dimers in order to bind to DNA. Presently, there is no conclusive evidence to indicate whether Nrf2 may activate gene expression as a homodimer or whether it is obligated to form heterodimeric complexes. Because p45 NF-E2, the first family member of these proteins, was found to dimerize with MafK in order to bind DNA and activate transcription (56), it was hypothesized that small Maf proteins may represent a partner for Nrf2 in effecting transcriptional activation (52). 

The relative rates of diffusion and reaction are important in the regulation of biochemical pathways. Transcription factors are proteins that bind to specialized regions of DNA and thereby facilitate transcription by RNA polymerase. The binding of one class of transcription factors, the basic leucine zipper (bZIP) proteins, is illustrated in Figure 4.30. The bZIP factors have a C-term-inal leucine zipper domain, a basic region that binds to DNA, and a domain that is important for transcriptional regulation. The bZIP factors must dimerize for transcriptional activity and, therefore, it is usually assumed that dimerization occurs before DNA binding (dimer pathway). A recent study shows... 

Nehl 427-560 Contains CNC and bZip regions ARE binding Dimerization with other bZip proteins (small Mafs) Contains nuclear localization and export signals Bloom et al. (2002) Itoh et al. (1999) Jain et al. (2005)... 

DNA binding domains called basic domains (rich in basic amino acids), occur in transcription factors in combination with leucine zipper or helix-loop-helix (HLH) dimerization domains (see below). The combination of basic domain and dimerization domain gives these proteins their names of basic leucine zipper proteins (bZIP) or basic HLH proteins, respectively. In each case the dimerization means that two basic domains (one from each monomer) interact with the target DNA. 

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