INTERACTION OF INVERTEBRATE MYOSINS WITH ACTIN

为了研究无脊椎动物肌肉的调节，我们分离了肌球蛋白， 从鲎的横纹肌-马蹄蟹和从 飞行肌肉的Lethocerus -一个水错误，并检查了滑动 肌动蛋白丝在纯化肌球蛋白上的速度。 知之甚少 关于如何调节龙蜥的飞行肌肉 我们的初步结果 表明粗（磷酸化）丝调节系统可能发挥作用， 一个重要的作用在Lethocerus飞行肌肉。 鲎横纹肌是 已知由瘦蛋白（肌钙蛋白和原肌球蛋白）和 粗（磷酸化）丝调节系统，其是钙- 依赖。 我们的实验表明， 系统是占主导地位的，肌动蛋白丝的运动发生， 磷酸化鲎肌球蛋白和活化的肌钙蛋白和原肌球蛋白 系统是必需的。 不同来源的原肌球蛋白似乎 当与肌动蛋白结合时，滑动速度增加5-10倍。 钙可以 在缺乏肌钙蛋白和 原肌球蛋白 鲎胰蛋白酶磷酸肽部分序列的测定 肌球蛋白轻链被肌球蛋白轻链磷酸化后 21 kD的链激酶产量ATS（PO 4）NVFAMFEQNQIA，和 SGS（PO 4）NVFSMFTE用于31 kD轻链。 比较序列 表明鲎磷酸化位点周围的序列 轻链更类似于脊椎动物平滑肌肌球蛋白的轻链 与脊椎动物横纹肌肌球蛋白轻链相比。

To study the regulation of invertebrate muscle, we isolated myosin both from the striated muscle of Limulus - the horseshoe crab and from the flight muscle of Lethocerus - a water bug, and examined the sliding velocity of actin filaments over the purified myosins. Little is known about the regulation of Lethocerus flight muscle. Our preliminary results show that the thick (phosphorylation) filament regulatory system may play an important role in Lethocerus flight muscle. Limulus striated muscle is known to be regulated by both the thin (troponin and tropomyosin) and thick (phosphorylation) filament regulatory systems which are calcium- dependent. Our experiments demonstrated that the "off" state of either system is dominant and for the movement of actin filaments to occur, both phosphorylated Limulus myosin and an activated troponin and tropomyosin system are required. Tropomyosin from different sources appeared to increase the sliding velocity 5-10 fold when bound to actin. Calcium does not alter the velocity significantly in the absence of both troponin and tropomyosin. Partial sequences of the tryptic phosphopeptides of Limulus myosin light chains following the phosphorylation by gizzard myosin light chain kinase yield ATS(PO4)NVFAMFEQNQIA for the 21 kD, and SGS(PO4)NVFSMFTE for the 31 kD light chain. Comparison of sequences suggests that the sequence around the phosphorylation site of Limulus light chains is more similar to that of vertebrate smooth muscle myosin light chain than to that of vertebrate striated muscle myosin light chain.