Low-temperature 1H-NMR evidence of the folding of isolated ribonuclease S-peptide

Abstract

The temperature (-7°C to 45°C, pH 5.4) and pH (0°C) dependence of 1H chemical shifts of ribonuclease S-peptide (5 mM, 1 M NaCl) has been measured at 360 MHz. The observed variations evidence the formation of a partial helical structure, involving the fragment Thr-3-Met-13. Two salt-bridges stabilize the helix: those formed by Glu-9-...His-12+ and Glu-2-...Arg-10+. The structural features deduced from the 1H-NMR at low temperature for the isolated S-peptide are compatible with the structure shown by the same molecule in the ribonuclease S crystal. © 1983.