Location of an α-Helix in Fragment 96–133 from Bovine Somatotropin by1H NMR Spectroscopy

Abstract

By use of two-dimensional NMR techniques most of the proton resonances (>90%) are assigned for the tryptic digest fragment 96–133 of bovine somatotropin in 30% 2,2,2-trifluoroethano-d3/70% H20. Qualitative analysis of the nuclear Overhauser enhancement (NOE) data indicates that a region of a-helix spans residues 106–128, while the N- and C-terminal regions assume nonregular structures. Amide-exchange rates and comparison of two-dimensional NOE spectra indicate that the most stable piece of helix spans residues 120–125 and that this piece of helix is stable in water at 25 °C. Evidence is given to support the fact that intermolecular association of the helical segments stabilizes the helix. © ..