Nature of the Intramolecular Fold in Alpha-Keratin and Alpha-Myosin

TLDR: The normal folded configuration a, the extended configuration β, and the reversible intramolecular transformation from a-keratin (or a-myosin) to β-kerATin (or β-myOSin) is the basis of the remarkable long-range elastic properties of this group of protein fibres.

Abstract: KERATIN, the protein of mammalian hairs and related epidermal tissues, the fibrous proteins of the epidermis itself, and myosin2, the principal protein of muscle tissue, all fall into one great group of fibrous proteins that have a common molecular configuration and similar long-range elastic properties. This generalization follows from a series of X-ray and supporting investigations that hare been described among other places in NATURE1. There will perhaps be no need then to summarize them again here, beyond recalling that the structural unit of the group is a ‘grid’ consisting of long polypeptide chains cross-linked by means of their side-chains, that the main-chains of this grid are not normally in the extended configuration but are thrown into a sequence of folds transverse to the side-chains, and that when the fibres are stretched the grid is pulled out flat, only to return to its folded configuration when the tension is released. The normal folded configuration we have called a, the extended configuration β, and the reversible intramolecular transformation from a-keratin (or a-myosin) to β-keratin (or β-myosin) is the basis of the remarkable long-range elastic properties of this group of protein fibres.