Yeast heat shock transcription factor N-terminal activation domains are unstructured as probed by heteronuclear NMR spectroscopy.

The structure and dynamics of the N-terminal activation domains of the yeast heat shock transcription factors of Kluyveromyces lactis and Saccharomyces cerevisiae were probed by heteronuclear 15N[1H] correlation and 15N[1H] NOE NMR studies. Using the DNA-binding domain as a structural reference, we show that the protein backbone of the N-terminal activation domain undergoes rapid, large-amplitude motions and is therefore unstructured. Difference CD data also show that the N-terminal activation domain remains random-coil, even in the presence of DNA. Implications for a "polypeptide lasso" model of transcriptional activation are discussed.