Nebulin is a full-length template of actin filaments in the skeletal muscle sarcomere: an immunoelectron microscopic study of its orientation and span with site-specific monoclonal antibodies.
Nebulin is a full-length template of actin filaments in the skeletal muscle sarcomere: an immunoelectron microscopic study of its orientation and span with site-specific monoclonal antibodies.
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Nebulin 是骨骼肌肌节中肌动蛋白丝的全长模板：使用位点特异性单克隆抗体对其方向和跨度进行免疫电子显微镜研究。
DOI：
10.1007/bf00297210
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发表时间：
1993
影响因子：
2.7
通讯作者：
Wang,K
中科院分区：
文献类型：
--
作者：
Wright,J;Huang,QQ;Wang,K
NeBulin是一种巨大的肌原纤维蛋白，在各种骨骼肌中的大小从700 kDa到900 kDa不等，它被认为构成了一组固定在Z线上的不可伸展的细丝，并与肌动蛋白细丝共同延伸。为了阐明这第四组肌丝在骨骼肌肌节中的结构组织，我们对一些针对已知序列位点的克隆的人星云蛋白片段的位置特异性单抗的表位进行了免疫电子显微镜定位。抗ND8的单抗N113标记了人股四头肌和兔腰大肌的Z线边缘，N113指向距离C末端约300个残基的片段。在人股四头肌和兔腰大肌中，N101单抗定位于距Z线0.89μm和0.80μm处，定位于N端附近的Nb5片段。此外，针对相邻片段NB5的羧侧片段Na3的单抗N109在兔腰大肌中定位于距Z线0.76μm处。表位位点和序列位点之间的这种一一对应关系表明，单个星云蛋白多肽跨越细丝的长度，其C-末端锚定在Z-线上。位点特异性抗体的表位间距与星云细丝的质量密度沿长度方向一致的概念一致。我们得出结论，根据电子显微镜的形态定义，细丝是由传统的肌动蛋白细丝(肌动蛋白/原肌球蛋白/肌钙蛋白)和可共扩展的星云蛋白多肽组成的复合丝，这些多肽充当全长分子模板，共同调节或稳定骨骼肌肌节中的肌动蛋白细丝。
Nebulin, a giant myofibrillar protein with size variants from 700 to 900 kDa in various skeletal muscles, has been proposed to constitute a set of inextensible filaments anchored at the Z-line and coextensive with actin filaments. To elucidate the architectural organization of this fourth set of myofilaments in the skeletal muscle sarcomere, we performed immunoelectron microscopic localization of epitope profiles of a number of site-specific monoclonal antibodies against cloned human nebulin fragments of known sequence loci. Monoclonal antibody N113, which is directed to fragment ND8 at approximately 300 residues away from the C-terminus, labelled the edges of Z-lines in both human quadriceps muscle and rabbit psoas muscle. Monoclonal antibody N101, which is directed to fragment NB5 near the N-terminal side, is localized to a single locus at 0.89 μm from the Z-line in human quadriceps muscle and 0.80μm from the Z-line in rabbit psoas muscle. Additionally, monoclonal antibody N109, which is directed to fragment NA3 on the carboxy side of the adjacent fragment NB5, is localized at 0.76 μm away from the Z-line in rabbit psoas muscle. This one-to-one correspondence between epitope loci and sequence loci demonstrates that a single nebulin polypeptide spans the length of the thin filament with its C-terminus anchored at the Z-line. The epitope spacings of site-specific antibodies are consistent with the notion that the nebulin filament is uniform in mass density along its length.We conclude that the thin filament, as defined morphologically by electron microscopy, is a composite filament of the conventional actin thin filament (actin/tropomyosin/troponin) and coextensible nebulin polypeptides which act as full-length molecular templates that regulate or stabilize colaterally the actin filament in the skeletal muscle sarcomere.