MOLECULAR PROPERTIES OF POST-MORTEM MUSCLE: EFFECT OF SULFHYDRYL REAGENTS AND POST-MORTEM STORAGE ON CHANGES IN MYOSIN B

Studies to determine the relationship of SH groups to certain changes of the myofibrillar proteins of post-mortem muscle were carried out with myosin B from at-death and post-mortem stored rabbit skeletal muscle (2° C and 25° C for 3 days) and with SH reagent modified myosin B from at-death and post-mortem stored muscle. Quantitative SH analysis, ATPase activity, turbidity rate and analytical ultracentrifugation were employed to determine the changes in myosin B associated with changes in SH groups. Post-mortem storage of muscle at 2°C for 3 days had no effect on SH content of myosin B; a decrease in SH groups, however, was observed in myosin B from muscle stored at 25°C for 3 days and for iodoacetamide (IAA) and N-ethylmaleimide (NEM) modified myosin B. ATPase activity was inhibited by reacting myosin B with enough NEM or IAA to block all SH groups. Dialysis of myosin B from at-death and post-mortem muscle against MCE to restore SH groups resulted in partial reversal of Mg++ and EGTA-activated ATPase of myosin B from post-mortem muscle and a less rapid rate of turbidity development. These results suggest that the state and nature of SH groups are partly involved in the actin-myosin interaction of post-mortem muscle; other constituents, however, in addition to SH groups are evidently modified and, in some instances, irreversibly modified, under certain post-mortem storage conditions.