Maruyama K, Matsuno A, Higuchi H, Shimaoka S, Kimura S, Shimizu T
Department of Biology, Faculty of Science, Chiba University, Japan.
J Muscle Res Cell Motil. 1989 Oct;10(5):350-9. doi: 10.1007/BF01758431.
Stretching of skinned fibres of frog skeletal muscle beyond the overlap of the thin and thick filaments followed by release to resting length results in disorganization of the thin filaments at the A-I junction of a sarcomere (Higuchi et al. (1988) J. Muscl. Res. Cell. Motility 9, 491-8). Immunoelectron microscopic observations showed that the binding sites of antibodies against connectin (titin) returned to the original position after extreme stretch and release but those of anti-nebulin antibodies were largely disorganized. The binding sites of anti-connectin antibodies moved within an I band with the change in sarcomere length, but those of anti-nebulin antibodies did not. Nebulin remained in the I band at extreme stretch. Thus connectin filaments appear to be responsible for maintaining mechanical continuity of a sarcomere and appear to behave independently of thin filaments. It is suggested that nebulin is localized in the I band but not in the A band and is associated with thin filaments but not with the elastic structure of myofibrils.
将青蛙骨骼肌的脱膜纤维拉伸至细肌丝和粗肌丝重叠范围之外，然后再释放至静息长度，这会导致肌节A-I连接处的细肌丝紊乱（Higuchi等人，(1988)《肌肉研究与细胞运动杂志》9, 491 - 498）。免疫电子显微镜观察显示，抗连接蛋白（肌联蛋白）抗体的结合位点在极度拉伸和释放后回到了原始位置，但抗伴肌动蛋白抗体的结合位点则大多紊乱。抗连接蛋白抗体的结合位点随肌节长度的变化在I带内移动，但抗伴肌动蛋白抗体的结合位点则不然。在极度拉伸时，伴肌动蛋白仍留在I带。因此，连接蛋白丝似乎负责维持肌节的机械连续性，并且其行为似乎独立于细肌丝。有人提出，伴肌动蛋白定位于I带而非A带，并且与细肌丝相关联，但与肌原纤维的弹性结构无关。
