Pu WT and Struhl K (1991) Highly conserved residues in the bZIP domain of yeast GCN4 are not essential for DNA binding. Mol Cell Biol 11(10):4918-26
Abstract: Yeast GCN4 and the Jun oncoprotein are transcriptional activators that bind DNA via a bZIP domain consisting of a leucine zipper dimerization element and an adjacent basic region that directly contacts DNA. Two highly conserved alanines (Ala-238 and Ala-239 in GCN4) and an invariant asparagine (Asn-235) in the basic region have been proposed to play important roles in DNA sequence recognition by bZIP proteins. Surprisingly, these conserved residues can be functionally replaced in GCN4 and in a derivative containing the Jun basic region (Jun-GCN4). The ability of an amino acid to functionally substitute for Asn-235 does not correlate with its preference for assuming the N-cap position of an alpha helix. This finding argues against the proposal of the scissors grip model that the invariant asparagine forms an N cap that permits the basic region to bend sharply and wrap around the DNA. In contrast to a prediction of the induced fork model, the pattern of functional substitutions of the conserved alanines together with the results of uracil interference experiments suggests that Ala-238 and Ala-239 do not make base-specific DNA contacts. Finally, the Jun-GCN4 chimeric proteins appear much more active in vivo than expected from their DNA-binding properties in vitro. The mechanistic and evolutionary implications of these results are discussed.
|Status: Published||Type: Journal Article | Research Support, Non-U.S. Gov't | Research Support, U.S. Gov't, P.H.S.||PubMed ID: 1922025|
Topics addressed in this paper
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|Protein Sequence Features|
|Protein-Nucleic Acid Interactions|
|Protein/Nucleic Acid Structure|