TROPONIN OF ASYNCHRONOUS FLIGHT-MUSCLE
TROPONIN OF ASYNCHRONOUS FLIGHT-MUSCLE
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DOI：
10.1016/0022-2836(88)90360-9
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发表时间：
1988-12-05
影响因子：
5.6
通讯作者：
FYRBERG, E
中科院分区：
文献类型：
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作者：
BULLARD, B;LEONARD, K;FYRBERG, E
肌钙蛋白是从Lethocerus（水蝽）的异步飞行肌肉中制备的，特别注意防止蛋白水解。调节复合物含有原肌球蛋白和肌钙蛋白成分。肌钙蛋白组分为Tn-C（18，000 Mr）、Tn-T（表观Mr 53，000）和重质组分Tn-H（表观Mr 80，000）。肌钙蛋白与原肌球蛋白紧密结合，在非变性条件下不能解离。肌钙蛋白T、肌钙蛋白H和原肌球蛋白的复合物抑制肌动球蛋白ATP酶的活性，在Ca ~（2+）存在下，这种抑制作用可被来自脊椎动物横纹肌的肌钙蛋白C解除。然而，与脊椎动物Tn-I不同，Tn-H本身不具有抑制作用。获得了抗Tn-T和Tn-H的单克隆抗体。用Tn-T抗体筛选果蝇cDNA λ噬菌体表达文库。确定编码蛋白质的cDNA序列，从而确定氨基酸序列。果蝇蛋白具有与脊椎动物骨骼和心脏Tn-T相似的序列。该序列延伸超过脊椎动物序列的羧基末端，并且最后40个残基是酸性的。果蝇Tn-T的部分序列与肌球蛋白轻链MLC-2的羧基端同源，并且一种抗Tn-T抗体与该轻链交叉反应。Lethocerus Tn-H与果蝇飞行肌的大型原肌球蛋白有关，其氨基酸序列是已知的，因为识别该组分的抗体也识别大型原肌球蛋白。Tn-H很容易被钙蛋白酶消化，这表明该分子的一部分具有延伸构型。负染标本的电子显微镜照片显示，Lethocerus细丝在约39 nm的间隔，这是没有看到从脊椎动物横纹肌细丝，可能是由于相对较大的肌钙蛋白复合物的投影。在僵硬条件下，肌球蛋白亚片段-1对细丝的装饰似乎不受肌钙蛋白的影响。异步飞行肌的肌钙蛋白缺乏脊椎动物横纹肌的Tn-I组分。Tn-H仅发生在飞行肌中，并且可能参与通过拉伸激活该肌肉。
Troponin has been prepared from the asynchronous flight muscle of Lethocerus (water bug) taking special care to prevent proteolysis. The regulatory complex contained tropomyosin and troponin components. The troponin components were Tn-C (18,000 Mr), Tn-T (apparent Mr 53,000) and a heavy component, Tn-H (apparent Mr 80,000). The troponin was tightly bound to tropomyosin and could not be dissociated from it in non-denaturing conditions. A complex of Tn-T, Tn-H and tropomyosin inhibited actomyosin ATPase activity and the inhibition was relieved by Tn-C from vertebrate striated muscle in the presence of Ca2+. However, unlike vertebrate Tn-I, Tn-H by itself was not inhibitory. Monoclonal antibodies were obtained to Tn-T and Tn-H. Antibody to Tn-T was used to screen an expression library of Drosophila cDNA cloned in lambda phage. The sequence of cDNA coding for the protein was determined and hence the amino acid sequence. The Drosophila protein has a sequence similar to that of vertebrate skeletal and cardiac Tn-T. The sequence extends beyond the carboxyl end of the vertebrate sequences, and the last 40 residues are acidic. Part of the sequence of Drosophila Tn-T is homologous to the carboxyl end of the Drosophila myosin light chain MLC-2 and one anti-Tn-T antibody cross-reacted with the light chain. Lethocerus Tn-H is related to the large tropomyosins of Drosophila flight muscle, for which the amino acid sequence is known, since antibodies that recognize this component also recognize the large tropomyosins. Tn-H is easily digested by calpain, suggesting that part of the molecule has an extended configuration. Electron micrographs of negatively stained specimens showed that Lethocerus thin filaments have projections at about 39 nm intervals, which are not seen on thin filaments from vertebrate striated muscle and are probably due to the relatively large troponin complex. Decoration of the thin filaments with myosin subfragment-1 in rigor conditions appeared not to be affected by the troponin. The troponin of asynchronous flight muscle lacks the Tn-I component of vertebrate striated muscle. Tn-H occurs only in the flight muscle and may be involved in the activation of this muscle by stretch.