STRUCTURE OF CONCANAVALIN-A AT 4.25-ANGSTROM RESOLUTION - (X-RAY DIFFRACTION/ELECTRON DENSITY MAP/ISOMORPHOUS REPLACEMENT/SUBUNITS/MOLECULAR WEIGHT)
STRUCTURE OF CONCANAVALIN-A AT 4.25-ANGSTROM RESOLUTION - (X-RAY DIFFRACTION/ELECTRON DENSITY MAP/ISOMORPHOUS REPLACEMENT/SUBUNITS/MOLECULAR WEIGHT)
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DOI：
10.1073/pnas.68.7.1393
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发表时间：
1971-01-01
影响因子：
11.1
通讯作者：
AINSWORTH, CF
中科院分区：
文献类型：
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作者：
HARDMAN, KD;WOOD, MK;AINSWORTH, CF
用三种同晶重原子衍生物的X射线衍射数据计算了伴刀豆球蛋白A的电子密度图，其值为4.25 μ m。晶体为正交晶系，晶胞尺寸分别为63.1、87.0和89.2 Ω fora、B和c。空间群为I222，每个晶胞有8个不对称单元。晶体不对称单元含有27，000道尔顿的蛋白质，并反映了寡聚体中的化学独特组分（原聚体）。单独的化学研究表明，原聚体由两条不同的多肽链组成。四个原聚体聚集在三个相互垂直的二重旋转轴的交叉点周围，形成108，000道尔顿的分子。该分子也可以细分为54，000道尔顿的两个原聚体单元。在两个原聚体单元内，连接原聚体的接触点明显多于形成整个分子的相邻两个原聚体单元之间的接触点。这些结果提供了一个可能的解释，在以前的ultracentralgal研究中获得的分子量的分歧。
An electron density map produced by x-ray diffraction analysis of concanavalin A has been calculated to 4.25 Å from data of three isomorphous heavy atom derivatives. The crystals are orthorhombic, with unit-cell dimensions of 63.1, 87.0, and 89.2 Å fora, b, andc, respectively. The space group is I222, with eight asymmetric units per unit cell. The crystal asymmetric unit contains 27,000 daltons of protein and reflects the chemically unique component (protomer) within the oligomer. Separate chemical studies indicate that the protomer consists of two different polypeptide chains. Four protomers cluster around the intersection of three mutually perpendicular two-fold rotation axes to form a molecule of 108,000 daltons. The molecule can also be subdivided into two-protomer units of 54,000 daltons. Within the two-protomer unit, there are significantly more contacts joining the protomers than there arebetweenadjacent two-protomer units that form the total molecule. These results provide a possible explanation for disagreement in molecular weights obtained in previous ultracentrifugal studies.