CD assays.

Circular dichroism (CD) spectroscopy experiments were performed on a Chirascan qCD spectrometer (Applied Photophysics) under a constant nitrogen flush; the spectrometer was equipped with a temperature control system (model TC125; Quantum Northwest). The concentrations of the proteins tested were set to 0.1 mg/ml in 20 mM Tris, pH 7.5. The resulting spectra were obtained at 1-nm intervals at 20°C using a cuvette with a path length of 1 mm, and three spectral scans with an integration time of 3 s per nm were averaged.