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 (PCMB-treated) and actomyosin (TNBS-treated actin and PCMB-treated myosin) suggested that certain thiol (SH) group ofcysteine residues in myosinand s-NH2groups 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 (< 1,000dyn/cm2) and at pH 5.4 (9,000dyn/cm2) of SH-blocked myosin was indicative of the major contribution of electrostatic interactions in the gelation of myosin. The effects of ATPon the gelation of myosin and actomyosin were also pH dependent. Total rod and LMMsub fragments of cardiac myosin formed respectively 2.6 times and 2-times stronger gel than produced by HMMsub fragments at identical conditions in the model system, but S-l sub fragment formed extremely weak gels under those conditions, which suggested the importance of the "tail" segment of the myosin molecule in the heat-induced gelation process.Amonganimal proteins, the gelling of col-lagen^and skeletal muscle actomyosin2~4) have been studied intensively in theory and practice. While collagen can form thermally reversible gels in a wide pH range and has no specific ionic requirement,5} myosin and actomyosin form irreversible gels on heating to a certain temperature and require specific pH and ionic conditions.6'7) Even the myosin from different types of skeletal muscle appears to vary in its requirements for forming gels of appreciable strength.8) However, information was altogether lacking on the heat-induced 63 gel formability of cardiac myosin and actomyosin complex.Our preceding paper9) provides information on the influence of pH, temperature, actin, and ionic and protein concentration on the heatinduced gel formation of cardiac myosin. This series describes the effects of ATP, SH-groups of myosin, and £-NH2 groups of actin on the gelling potential of cardiac myosin and actomyosih complexes. Wealso a compared the gel strength of myosin and reconstituted actomyosin from cardiac and skeletal muscle under various conditions in a model system.

Protein Extractability and Thermally Induced Gelation Properties of Myofibrils Isolated from Pre‐ and Postrigor Chicken Muscles

“…SSP of the postrigor muscle would be expected to contain more actomyosin, which may largely determine gelation properties, than SSP from the prerigor muscle. Yasui et al (1982) and Samejima et al (1988) have shown that gel strength of mixed actomyosin and myosin varies, depending on the myosinlactomyosin ratio.…”

“…Muscle protein gelation is one of the most important functional properties contributing to the textural quality of many processed meats (Siegel and Schmidt, 1979;Acton et al, 1983). Although the mechanism of myosin gelation has been extensively studied (Yasui et al, 1980(Yasui et al, , 1982Asghar et al, 1984;Samejima et al, 1986Samejima et al, , 1988Yamamoto et al, 1988) is known about gelation of myofibrils, a complex system of muscle proteins. Because prerigor myofibrils (mainly uncomplexed myosin and actin) are expected to contain a different protein composition than postrigor myofibrils (primarily actomyosin), they would likely show different gelation behavior.…”

Effect of trehalose on the gel-forming ability, state of water and myofibril denaturation of horse mackerel Trachurus japonicus surimi during frozen storage

“…In contrast, Mf Ca‐ATPase activity declined tremendously by 135 days of storage compared to other parameters. This contradiction could be explained by the cause that Mf Ca‐ATPase activity doesn’t reflect the denaturation of myosin rod which is known to be important for gel formation 33,34 as well as inflexible in frozen storage conditions 35 …”