扇贝肌钙蛋白及其对肌球蛋白超沉淀的影响

分离了扇贝闭壳肌肌钙蛋白，其分子量为４６（ＩｎＩ），４０（ＴｎＴ），和２２（ＴｎＣ）ｋＤ．肌球蛋白Ｂ含有主要的收缩蛋白质与调节蛋白质，在有Ｃａ２＋和ＡＴＰ存在时，它会发生超沉淀作用．经低离子强度溶液反复沉淀处理，即失去Ｃａ２＋－敏感性，成为去敏肌球蛋白Ｂ．在Ｃａ２＋和ＡＴＰ作用下，它仍可发生超沉淀作用，但仅及最大活性的５０％．若加入肌钙蛋白，则反应活性可完全恢复．兔骨骼肌肌钙蛋白可替代扇贝闭壳肌肌钙蛋白．这表明扇贝闭壳肌兼有肌动蛋白相关调节和肌球蛋白相关调节．

Troponin of Scallop Adductor Muscle and its Effect on Myosin B Superprecipitation

Troponins with molecular weights of 46(TnI),40(TnT)and 22 (TnC)kD have been isolated from scallop adductor muscle.In the presence of Ca 2 and ATP,scallop myosin B,containing major contractile and regulatory proteins,can produce superprecipitation,showing two maximal pH,Ca 2 sensitivity and substrate inhibition.After washing with low ionic strength solution several times,myosin B loses Ca 2 sensitivity and becomes a desensitized myosin B.Ca 2 and ATP can still induce its superprecipitation by 50 percent of maximal activity.Adding scallop troponins into reaction system,the desensitized myosin B can restore superprecipitation completely.In addition,rabbit skeletal troponins can substitute for scallop adductor troponins in inducing myosin B superprecipitation.The results suggest that the actin linked and myosin linked regulatory mechanisms coexist in scallop adductor muscle.