Circular Dichroism.

CD experiments were carried out on a J-810 spectropolarimeter (JASCO Corp., Tokyo, Japan) equipped with a Peltier system for temperature control using a 0.1 cm path length cuvette. The CD spectra shown in figure 5A have been measured on 12.3 μM solution of Nat and Pol NS in 50 mM KCl, 10 mM Tris-HCl, pH 8.0, with or without incubation with EMB. NS samples were incubated in saturated EMB solution as described above and then washed by spin columns to remove excess EMB before collecting the CD spectrum. The Pol NS samples (with or without EMB) were formed upon incubation of Nat solution at 55 °C for two hours, residual monomeric NS was removed by spin columns (cut-off 100kDa). All measurements were performed at pH 8.0, 20 °C, with an optical path of 0.1 cm.

For the temperature ramp experiments, ellipticity at 218 nm wavelength was recorded from 20 to 95 °C (temperature slope 1.0 °C/min) on NS samples (Nat, Lat and Cle with or without EMB) in 50 mM KCl, 10 mM Tris-HCl, pH8.0, at a NS concentration of 0.25 mg/ml. NS samples were incubated for 30 minutes at 4 °C in a saturated EMB solution, then centrifuged for 10 minutes at 20000 rcf before starting the temperature ramps.