The G-H turn region of myoglobin acts as a helix stop signal

A study of peptide fragments of sperm whale myoglobin, corresponding to the region between the G- and H- helices, in water and solvent mixtures of water and trifluoroethanol (TFE) indicates that turn sequences in proteins help in helix termination in TFE during the initial folding stages in the native protein. Mb-GH5 (Myoglobin-GH5), a five residue peptide, and Mb-GH25, a 25 residue peptide, turn conformation in aqueous solutions though there is no helix formation in the regions on either side of the residue sequence. The studies used circular dichroism (CD) and nuclear magnetic resonance spectroscopy (NMR) techniques.