Wang S M, Greaser M L
J Muscle Res Cell Motil. 1985 Jun;6(3):293-312. doi: 10.1007/BF00713171.
A monoclonal antibody specific to bovine cardiac titin has been identified. The antibody recognizes a common antigenic site in striated muscles of several species. In relaxed myofibrils, specific staining at the A-I junction resulted in a doublet of fluorescent bands within a sarcomere. The distance between the doublets in successive sarcomeres varied according to the degree of myofibrillar contraction. Staining on formamide-extracted myofibrils has confirmed that this epitope is located near the outer edges of isolated A bands. Selective extraction of myofibrillar proteins resulted in different staining patterns. Disrupting the structural integrity of the M-line or the A-band centre caused a significant amount of titin to translocate toward the Z-line region. In contrast, shortening of the A-band by removal of myosin from the ends of the thick filaments resulted in anti-titin staining moving closer to the M-line region. Several conclusions can be drawn from this study: (a) two aligned groups of titin molecules are placed symmetrically to the M-line in a sarcomere; (b) titin may attach directly or via intermediary protein(s) to sites near the M-line and Z-line such that the protein is under tension and (c) removal of proteins from either region results in titin staining in the opposite region. However, the edges of the A-band give some hindrance to collapse of the titin toward the M-line.
已鉴定出一种对牛心肌肌联蛋白具有特异性的单克隆抗体。该抗体识别几种物种横纹肌中的一个共同抗原位点。在松弛的肌原纤维中，A-I交界处的特异性染色在一个肌节内产生了一对荧光带。连续肌节中这对荧光带之间的距离根据肌原纤维收缩程度而变化。对经甲酰胺处理的肌原纤维进行染色证实，该表位位于分离的A带的外边缘附近。肌原纤维蛋白的选择性提取导致了不同的染色模式。破坏M线或A带中心的结构完整性会导致大量肌联蛋白向Z线区域移位。相反，通过从粗肌丝末端去除肌球蛋白使A带缩短，会导致抗肌联蛋白染色向M线区域靠近。从这项研究中可以得出几个结论：（a）两组对齐的肌联蛋白分子在肌节中相对于M线对称排列；（b）肌联蛋白可能直接或通过中间蛋白附着在M线和Z线附近的位点，从而使该蛋白处于张力之下；（c）从任一区域去除蛋白质都会导致肌联蛋白在相反区域染色。然而，A带的边缘对肌联蛋白向M线的塌陷有一定阻碍。
