Labeit S, Barlow D P, Gautel M, Gibson T, Holt J, Hsieh C L, Francke U, Leonard K, Wardale J, Whiting A
European Molecular Biology Laboratory, Heidelberg, FRG.
Nature. 1990 May 17;345(6272):273-6. doi: 10.1038/345273a0.
Titin is the largest polypeptide yet described (relative molecular mass approximately 3 x 10(6); refs 1, 2) and an abundant protein of striated muscle. Its molecules are string-like and in vivo span from the M to Z-lines. I-band regions of titin are thought to make elastic connections between the thick filament and the Z-line, thereby forming a third type of sarcomere filament. These would centre the A-band in the sarcomere and provide structural continuity in relaxed myofibrils. The A-band region of titin seems to be bound to the thick filament, where it has been proposed to act as a 'molecular ruler' regulating filament length and assembly. Here, we show that partial titin complementary DNAs encode a regular pattern of two types of 100-residue motif, each of which probably folds into a separate domain type. Such motifs are present in several evolutionarily divergent muscle proteins, all of which are likely to interact with myosin. One or both of the domain types is therefore likely to bind to myosin.
肌联蛋白是目前已描述的最大的多肽（相对分子质量约为3×10⁶；参考文献1、2），是横纹肌中的一种丰富蛋白质。其分子呈线状，在体内从M线延伸至Z线。肌联蛋白的I带区域被认为在粗肌丝和Z线之间形成弹性连接，从而形成第三种类型的肌节细丝。这些细丝将A带定位于肌节中心，并在松弛的肌原纤维中提供结构连续性。肌联蛋白的A带区域似乎与粗肌丝结合，有人提出它在那里充当调节细丝长度和组装的“分子尺”。在此，我们表明部分肌联蛋白互补DNA编码两种100个残基基序的规则模式，每种基序可能折叠成一种单独的结构域类型。这种基序存在于几种进化上不同的肌肉蛋白中，所有这些蛋白都可能与肌球蛋白相互作用。因此，这两种结构域类型中的一种或两种可能与肌球蛋白结合。
