The bZIP class of eukaryotic transcriptional regulators utilize a distinct structural motif that consists of a leucine zipper that mediates dimerization and an adjacent basic region that directly contacts DNA. Although models of the protein-DNA complex have been proposed, the basis of DNA-binding specificity is essentially unknown. By genetically selecting for derivatives of yeast GCN4 that activate transcription from promoters containing mutant binding sites, we isolate an altered-specificity mutant in which the invariant asparagine in the basic region of bZIP proteins (Asn-235) has been changed to tryptophan. Wild-type GCN4 binds the optimal site (ATGACTCAT) with much higher affinity than the mutant site (7TGACTCAA), whereas the Trp-235 protein binds these sites with similar affinity. Moreover, the Trp-235, Ala-235, and Gln-235 derivatives differ from GCN4 in their strong discrimination against GTGACTCAC. These results suggest a direct interaction between Asn-235 and the ±4 position of the DNA target site and are discussed in terms of the scissors-grip and induced-fork models of bZIP proteins.
CITATION STYLE
Tzamarias, D., Pu, W. P., & Struhl, K. (1992). Mutations in the bZIP domain of yeast GCN4 that alter DNA-binding specificity. Proceedings of the National Academy of Sciences of the United States of America, 89(6), 2007–2011. https://doi.org/10.1073/pnas.89.6.2007
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