Sodek J, Hodges R S, Smillie L B, Jurasek L
Proc Natl Acad Sci U S A. 1972 Dec;69(12):3800-4. doi: 10.1073/pnas.69.12.3800.
A tentative amino-acid sequence for the COOH-terminal half of rabbit skeletal tropomyosin is reported. These studies confirm our previous conclusions that this tropomyosin consists of several different but similar polypeptide chains. In the sequence, nonpolar residues occur in two series at intervals of seven residues. Amino-acid residues in series I are three residues on the NH(2)-terminal side of, and four residues on the COOH-terminal side of, residues in series II. The presence of occasional charged or ambivalent residues in the positions of series I or II does not lead to a disruption of this long-range pattern. The majority of residues located between the nonpolar residues are charged or polar amino acids. Two highly similar or identical alpha-helices with the reported sequence can be packed together in parallel in a coiled-coil structure. These may be in register or staggered by seven residues or some multiple of it. The observation that groups of small hydrophobic side chains appear to alternate with groups of bulky side chains suggests that a staggered arrangement of the two alpha-helices would maximize the regularity and hydrophobic interactions of the coiled-coil. Model building considerations show that this would occur with a stagger of 14 residues. Such an arrangement could account for the end-to-end aggregation of tropomyosin in solution, and in crystal and tactoid filaments. However, a structure in which the two polypeptides are in register cannot be ruled out.
本文报道了兔骨骼肌原肌球蛋白COOH末端一半的初步氨基酸序列。这些研究证实了我们之前的结论，即这种原肌球蛋白由几条不同但相似的多肽链组成。在该序列中，非极性残基以七个残基的间隔出现在两个系列中。系列I中的氨基酸残基位于系列II中残基的NH(2)末端一侧三个残基处，以及COOH末端一侧四个残基处。系列I或II位置上偶尔出现的带电荷或两性残基不会导致这种长程模式的破坏。位于非极性残基之间的大多数残基是带电荷或极性氨基酸。具有所报道序列的两个高度相似或相同的α螺旋可以以平行方式堆积在卷曲螺旋结构中。它们可能是对齐的，或者错开七个残基或其某个倍数。小疏水侧链基团似乎与大侧链基团交替出现的观察结果表明，两个α螺旋的错开排列将使卷曲螺旋的规则性和疏水相互作用最大化。模型构建考虑表明，这将在错开14个残基时发生。这种排列可以解释原肌球蛋白在溶液中以及在晶体和类晶体细丝中的端对端聚集。然而，不能排除两条多肽对齐的结构。
