Itoh Takafumi, Garcia Roberta N, Adachi Motoyasu, Maruyama Yukie, Tecson-Mendoza Evelyn Mae, Mikami Bunzo, Utsumi Shigeru
Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
Acta Crystallogr D Biol Crystallogr. 2006 Jul;62(Pt 7):824-32. doi: 10.1107/S090744490601804X. Epub 2006 Jun 20.
The 8S globulins of mung bean [Vigna radiata (L.) Wilczek] are vicilin-type seed storage globulins which consist of three isoforms: 8Salpha, 8Salpha' and 8Sbeta. The three isoforms have high sequence identities with each other (around 90%). The structure of 8Salpha globulin has been determined for the first time by X-ray crystallographic analysis and refined at 2.65 A resolution with a final R factor of 19.6% for 10-2.65 A resolution data. The refined 8Salpha globulin structure consisted of 366 of the 423 amino-acid residues (one subunit of the biological trimer). With the exception of several disordered regions, the overall 8Salpha globulin structure closely resembled those of other seed storage 7S globulins. The 8Salpha globulin exhibited the highest degree of sequence identity (68%) and structural similarity (a root-mean-square deviation of 0.6 A) with soybean beta-conglycinin beta (7S globulin). Their surface hydrophobicities are also similar to each other, although their solubilities differ under alkaline conditions at low ionic strength. This difference seems to be a consequence of charge-charge interactions and not hydrophobic interactions of the surfaces, based on a comparison of the electrostatic potentials of the molecular surfaces. The thermal stability of 8Salpha globulin is lower than that of soybean beta-conglycinin beta. This correlates with the cavity size derived from the crystal structure, although other structural features also have a small effect on the protein's thermal stability.
绿豆[Vigna radiata (L.) Wilczek]的8S球蛋白是豌豆球蛋白型种子贮藏球蛋白，由三种异构体组成：8Sα、8Sα'和8Sβ。这三种异构体彼此具有较高的序列同一性（约90%）。8Sα球蛋白的结构首次通过X射线晶体学分析确定，并在2.65 Å分辨率下进行了精修，对于10 - 2.65 Å分辨率的数据，最终R因子为19.6%。精修后的8Sα球蛋白结构由423个氨基酸残基中的366个组成（生物三聚体的一个亚基）。除了几个无序区域外，8Sα球蛋白的整体结构与其他种子贮藏7S球蛋白的结构非常相似。8Sα球蛋白与大豆β-伴大豆球蛋白β（7S球蛋白）表现出最高程度的序列同一性（68%）和结构相似性（均方根偏差为0.6 Å）。它们的表面疏水性也彼此相似，尽管在低离子强度的碱性条件下它们的溶解度不同。基于分子表面静电势的比较，这种差异似乎是表面电荷 - 电荷相互作用的结果，而不是疏水相互作用的结果。8Sα球蛋白的热稳定性低于大豆β-伴大豆球蛋白β。这与从晶体结构得出的腔大小相关，尽管其他结构特征对蛋白质的热稳定性也有较小的影响。
