Basic leucine zipper (bZIP) domain of Plant G-box binding factor 1 (GBF1)-like transcription factors: a DNA-binding and dimerization domain
This subfamily is composed of plant bZIP transciption factors including Arabidopsis thaliana G-box binding factor 1 (GBF1), Zea mays Opaque-2 and Ocs element-binding factor 1 (OCSBF-1), Triticum aestivum Histone-specific transcription factor HBP1 (or HBP-1a), Petroselinum crispum Light-inducible protein CPRF3 and CPRF6, and Nicotiana tabacum BZI-3, among many others. bZIP G-box binding factors (GBFs) contain an N-terminal proline-rich domain in addition to the bZIP domain. GBFs are involved in developmental and physiological processes in response to stimuli such as light or hormones. Opaque-2 plays a role in affecting lysine content and carbohydrate metabolism, acting indirectly on starch/amino acid ratio. bZIP factors act in networks of homo and heterodimers in the regulation of a diverse set of cellular processes. The bZIP structural motif contains a basic region and a leucine zipper, composed of alpha helices with leucine residues 7 amino acids apart, which stabilize dimerization with a parallel leucine zipper domain. Dimerization of leucine zippers creates a pair of the adjacent basic regions that bind DNA and undergo conformational change. Dimerization occurs in a specific and predictable manner resulting in hundreds of dimers having unique effects on transcription.
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