Field J M, Tatham A S, Shewry P R
M.M.G. Agriseed, Norfolk.
Biochem J. 1987 Oct 1;247(1):215-21. doi: 10.1042/bj2470215.
A high-Mr subunit was prepared from durum wheat (Triticum durum). Viscometric analysis showed that the molecule is rod-shaped, with molecular dimensions of about 50 nm x 1.75 nm (500 A x 17.5 A) in 0.05 M-acetic acid/0.01 M-glycine and 49 nm x 1.79 nm (490 A x 17.9 A) in aq. 50% (v/v) propan-1-ol (+/- 0.01 M-glycine) at 30 degrees C. C.d. spectroscopy in the same solvents indicated the presence of beta-turns, but little alpha-helix [7% in 50% (v/v) propan-1-ol] and no beta-sheet. However, when dissolved in trifluoroethanol the protein contains about 30% alpha-helix, and viscometric analysis gives dimensions of about 62 nm x 1.53 nm (620 A x 15.3 A). It is proposed, on the basis of these studies and previously published structural prediction, that the repetitive central domain of the high-Mr subunit forms a loose spiral based on repetitive beta-turns, whereas the shorter non-repetitive N- and C-terminal domains are alpha-helical in trifluoroethanol, but random coil in other solvents. The Mr of the high-Mr subunit determined from the intrinsic viscosity in 6.0 M-guanidinium chloride was 65,000, compared with 84,000 determined in 5.0 M-guanidinium thiocyanate. The latter value is consistent with the Mr values for related proteins whose complete amino acid sequences are known, and it was concluded that the protein is incompletely denatured in the former solvent. This was confirmed by c.d. spectroscopy in increasing concentrations (1-6 M) of guanidinium chloride.
从硬粒小麦（Triticum durum）中制备了一种高分子量亚基。粘度分析表明，该分子呈棒状，在0.05 M-乙酸/0.01 M-甘氨酸中分子尺寸约为50 nm×1.75 nm（500 Å×17.5 Å），在30℃下50%（v/v）丙醇（±0.01 M-甘氨酸）水溶液中为49 nm×1.79 nm（490 Å×17.9 Å）。在相同溶剂中的圆二色光谱表明存在β-转角，但几乎没有α-螺旋[在50%（v/v）丙醇中为7%]且没有β-折叠。然而，当溶解在三氟乙醇中时，该蛋白质含有约30%的α-螺旋，粘度分析给出的尺寸约为62 nm×1.53 nm（620 Å×15.3 Å）。基于这些研究和先前发表的结构预测，有人提出，高分子量亚基的重复中心结构域基于重复的β-转角形成松散的螺旋，而较短的非重复N-和C-末端结构域在三氟乙醇中是α-螺旋的，但在其他溶剂中是无规卷曲的。由6.0 M-氯化胍中的特性粘度测定的高分子量亚基的Mr为65,000, 而在5.0 M-硫氰酸胍中测定的为84,000。后一个值与已知完整氨基酸序列的相关蛋白质的Mr值一致，并且得出结论，该蛋白质在前一种溶剂中未完全变性。这通过在浓度逐渐增加（1-6 M）的氯化胍中的圆二色光谱得到证实。
