Freeze Denaturation of Carp Myosin Subfragment-1 as Compared with Thermal Denaturation

Abstract

Denaturation process of carp subfragment-1 (S-1) during frozen storage at -20°C was investigated by comparing with thermal denaturation. Frozen storage of S-1 inactivated the Ca²⁺-ATPase activity, while the S-1 solution exhibited no turbidity. Centrifugation of the frozen S-1 sedimented a very small amount of S-l demonstrating that inactivated S-1 was still soluble. Sepharose CL-4B gel filtration demonstrated that the inactivated S-1 by freezing was eluted at the ascending part of single peak of S-1 indicating that a very small structural change was brought about by inactivation. The inactivated S-1 by freezing still retained light chain binding ability. These were completely different from those observed with thermally denatured S-1. Thus, freeze denaturation of S-1 was characterized by the retained LC binding ability resulted in a prevention of aggregate formation. Tryptic digestion of frozen S-1 revealed that inactivated S-1 was unspecifically cleaved into short pieces.