Studies on heat-induced gelation of cardiac myosin and actomyosin. Part II. Effects of SH groups, .EPSILON.-NH2 groups, ATP, and myosin subfragments on heat-induced gelling of cardiac myosin and comparison with skeletal myosin and actomysin gelling capacity.

Abstract

Heat-induced gelling characteristics of myosin-actin from cardiac and skeletal muscle were investigated under various conditions in a model system. The interaction between actin and myosin at weight ratios of 1:15 ~ 1: 9 from cardiac or skeletal muscle seemed to contribute to heat-induced gel strength at pH 6.0, but such interaction seemed to carry little significance in gel formation at pH 5.4.A decrease in gel rigidity of chemically modified myosin (PC MB-treated) and actomyosin (TNBS-treated actin and PCMB-treated myosin) suggested that certain thiol (SH) group of cysteine residues in myosin and ɛ-NH2 groups of lysine residues in actin were involved in the development of gel on heating. However, the magnitude of difference in gel strength at pH 6.0 (< 1,000 dyn/cm2) and at pH 5.4 (9,000 dyn/cm2) of SH-blocked myosin was indicative of the major contribution of electrostatic interactions in the gelation of myosin. The effects of ATP on the gelation of myosin and actomyosin were also pH dependent.Total ro...