Structural characterization of a minimal functional transactivation domain from the human glucocorticoid receptor.
A 58-amino acid polypeptide containing the functional core region, the tau 1 core, of the major transactivation domain of the human glucocorticoid receptor has been expressed in Escherichia coli and purified to homogeneity. The polypeptide retains 60-70% of the activity of the intact domain when assayed in vivo or in vitro. This report describes a structural characterization of the tau 1 core peptide fragment. Circular dichroism spectroscopy shows that the tau 1 core and a larger fragment encompassing the intact tau 1 domain are largely unstructured in water solution under a variety of pH conditions. The tau 1 core, however, acquires a significant alpha-helical structure when analyzed in the presence of trifluoroethanol, an agent that favors secondary structure formation in regions that have propensity for alpha-helical conformation. Two- and three-dimensional NMR spectroscopy of 15N-labeled tau 1 core, in the presence of trifluoroethanol, has allowed sequential assignment of 1H and 15N resonances and identification of three protein segments with alpha-helical character. Potentially helix-breaking proline substitutions, in proposed alpha-helical regions, lead to reduced activity, suggesting that alpha-helices are important for transactivation in vivo.
Dahlman-Wright
K
K
Centre for Structural Biochemistry, Karolinska Institutet, Novum Huddinge, Sweden.
Baumann
H
H
McEwan
I J
IJ
Almlöf
T
T
Wright
A P
AP
Gustafsson
J A
JA
Härd
T
T
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017433:Protein Structure, Secondary; D011965:Receptors, Glucocorticoid / Q000737:chemistry*; D012441:Saccharomyces cerevisiae; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000737:chemistry*; D015533:Transcriptional Activation
D011965:Receptors, Glucocorticoid; D015534:Trans-Activators