The NH2 terminus of titin spans the Z-disc: its interaction with a novel 19-kD ligand (T-cap) is required for sarcomeric integrity.
The NH2 terminus of titin spans the Z-disc: its interaction with a novel 19-kD ligand (T-cap) is required for sarcomeric integrity.
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DOI：
10.1083/jcb.143.4.1013
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发表时间：
1998-11-16
期刊：
影响因子：
--
通讯作者：
Labeit S
中科院分区：
文献类型：
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作者：
Gregorio CC;Trombitás K;Centner T;Kolmerer B;Stier G;Kunke K;Suzuki K;Obermayr F;Herrmann B;Granzier H;Sorimachi H;Labeit S
肌联蛋白是脊椎动物横纹肌中的巨大弹性蛋白，具有前所未有的3-4兆道尔顿的分子量。肌联蛋白的单分子从Z线延伸到M线。在这里，我们定义了肌联蛋白在Z线内的分子布局;最NH 2-末端30 kD的肌联蛋白位于相邻肌节边界处的Z线外围，而随后的60 kD肌联蛋白跨越Z线的整个宽度。体外结合研究表明，哺乳动物肌联蛋白的Z-线跨越区至少有4个潜在的α-辅肌动蛋白结合位点。肌联蛋白细丝可以通过改变其NH 2-末端重叠的长度和用于交联肌联蛋白和细丝的α-辅肌动蛋白结合位点的数量来指定Z线宽度和内部结构。此外，我们证明，NH 2-末端肌联蛋白IG重复Z1和Z2在周边的Z线结合到一个新的19 kD的蛋白质，称为肌联蛋白帽。在心肌细胞中使用显性负性方法，肌联蛋白Z1-Z2结构域和肌联蛋白帽被证明是肌节结构完整性所需的，这表明它们的相互作用在肌联蛋白介导的肌节组装中是至关重要的。
Titin is a giant elastic protein in vertebrate striated muscles with an unprecedented molecular mass of 3–4 megadaltons. Single molecules of titin extend from the Z-line to the M-line. Here, we define the molecular layout of titin within the Z-line; the most NH2-terminal 30 kD of titin is located at the periphery of the Z-line at the border of the adjacent sarcomere, whereas the subsequent 60 kD of titin spans the entire width of the Z-line. In vitro binding studies reveal that mammalian titins have at least four potential binding sites for α-actinin within their Z-line spanning region. Titin filaments may specify Z-line width and internal structure by varying the length of their NH2-terminal overlap and number of α-actinin binding sites that serve to cross-link the titin and thin filaments. Furthermore, we demonstrate that the NH2-terminal titin Ig repeats Z1 and Z2 in the periphery of the Z-line bind to a novel 19-kD protein, referred to as titin-cap. Using dominant-negative approaches in cardiac myocytes, both the titin Z1-Z2 domains and titin-cap are shown to be required for the structural integrity of sarcomeres, suggesting that their interaction is critical in titin filament–regulated sarcomeric assembly.