The dissociation and reassociation of the subunit polypeptide chains of myosin.

Recent studies on the behavior of myosin in solutions of guanidine.HCl (1) and urea (2) have shown this protein to consist of three subunit chains of apparently identical mass and electrophoretic mobility. Moreover, results obtained from paper chromatographic and electrophoretic separation of the tryptic peptides of myosin suggest that the three chains are closely similar, if not identical, in their primary structures (3). The present study is directed toward an understanding of the molecular dissociation observed in concentrated aqueous guanidine.HCl solutions as assessed by optical rotation, viscosity, sedimentation, and adenosine triphosphatase activity. The reverse of this dissociation-unfolding process, i.e. removal of guanidine. HCl from guanidine + HCl-myosin solutions has also been examined with a view to understanding the requirements for reformation of the native secondary and tertiary structures of complex, multistranded protein molecules.