The Interaction of Detergents with Proteins

The Effect of Detergents on the Conformation of Bacillus subtilis α-Amylase and Bence-Jones Protein

抄録

The effects of three different kinds of detergents, namely, anionic, cationic and nonionic detergents, on the conformation of two different proteins were studied by the measurements of optical rotatory disperson and ultraviolet spectra and infrared spectra as functions of pH and concentration of the detergents. One of the protein examined is bacterial α-amylase which has a folded structure of single poly-peptide chain without disulfide linkage. The other one is Bence-Jones protein which may contain an intramolecular β-structure but not an α-helix. The experimental results revealed that change in optical rotatory dispersion by adding detergent was due to destruction of the original conformation followed by a partial α-helix formation of the unfolded poly-peptide chain, and that the extent of the α-helix formed depends upon the pH value. This refolded polypeptide chain was imbeded in a hydrophobic fabric produced by deter-gent associated around the polypeptide. An-ionic and cationic detergents act as a helix former even at extremely alkaline or acid pH region. On the other hand, nonionic detergent has not such an action throughout the pH region studied.
The authors wish to thank Dr. K. Hamaguchi for his helpfull discussions during this work, Dr. K. Fukushima for his valuable advices on the interpretation of infrared spectral data and also Mr. H. Matsuura for the measurements of infrared spectra. The authors are also indebted to Dr. S. Migita for the generous gift of Bence Jones protein which made this work possible and to Mr. H. Tokiwa (Kao Soap Co., Ltd.) for the gifts of detergents.