Chaperones in progesterone receptor complexes.

Studying the components, pathways, and dynamics of progesterone receptor (PR) assembly with chaperones has provided a highly valuable model system for understanding the coordinate actions of chaperones. Chaperones are primarily adapted to facilitate protein folding processes, and the actions of chaperones toward PR and other steroid receptors probably remain within this general functional boundary. Unlike a typical misfolded protein substrate, PR's folding is effectively arrested prior to hormone binding, thus extending indefinitely the chaperone-interaction phase that normally would be transitory during progressive protein folding. While one could consider this a limitation in PR's ability to fold properly, perhaps a more accurate view is that PR is specially adapted to remain 'misfolded', and thus extend chaperone interactions that function efficiently in repressing PR's transcriptional activity while the receptor awaits an activating signal. Copyright 2000 Academic Press.