An alternative to the coiled-coil for α-fibrous proteins

Abstract

The molecular conformation adopted by the α -fibrous proteins such as paramyosin and α -keratin is commonly accepted as based on the coiled-coil rope suggested by Crick and by Pauling and Corey. Recent work has cast some doubt as to whether the coiled-coil model as postulated is sufficient to explain the X-ray diffraction patterns completely. An alternative system is described where the axes of the α -helices are straight. In this case, regular amino acid sequences are required and the side chains have a different symmetry from the main chain backbone. The observed spacings of the 1·5 and 5·1 A meridional reflections as well as the near-equatorial layer line streak observed in the diffraction patterns can be easily explained in terms of such a model.