CRYSTALLOGRAPHIC REFINEMENT AND ATOMIC MODELS OF A HUMAN FC FRAGMENT AND ITS COMPLEX WITH FRAGMENT-B OF PROTEIN-A FROM STAPHYLOCOCCUS-AUREUS AT 2.9-A AND 2.8-A RESOLUTION
CRYSTALLOGRAPHIC REFINEMENT AND ATOMIC MODELS OF A HUMAN FC FRAGMENT AND ITS COMPLEX WITH FRAGMENT-B OF PROTEIN-A FROM STAPHYLOCOCCUS-AUREUS AT 2.9-A AND 2.8-A RESOLUTION
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DOI：
10.1021/bi00512a001
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发表时间：
1981-01-01
期刊：
影响因子：
2.9
通讯作者：
DEISENHOFER, J
中科院分区：
文献类型：
--
作者：
DEISENHOFER, J
人Fc片段的模型在2.9埃下精制。分辨率使用两种不同的自动化程序进行晶体学精修。最终R值为0.22。CH 3结构域的二聚体非常类似于Fab片段中的CH 1-CL聚集体。CH 2结构域之间没有接触。CH 2和CH 3结构域之间的接触具有约1/3的CH 3-CH 3接触的大小。碳水化合物是9个己糖单元的支链，覆盖了CH 2结构域的部分C-接触面，屏蔽了该表面上的疏水残基。碳水化合物的六个原子在CH 2结构域中的原子的氢键距离内。对S. A蛋白的Fc片段与片段B复合物的晶体学进行了精细化。金黄色葡萄球菌将模型的R值降低至0.24。片段B的结构的主要部分由2 α-螺旋;多肽链的其余部分不规则地折叠。在晶体中，片段B与Fc片段分子形成2个接触。接触1涉及来自片段B的两个螺旋的残基和来自Fc的CH 2和CH 3结构域的残基，并且主要是疏水性的。触点2小于触点1。来自第二螺旋的残基和片段B的相邻残基以及仅来自Fc的CH 3结构域的残基有助于接触2。接触2的性质主要是极性的，并且包括硫酸根离子。有强有力的论据表明，接触1是在生理条件下在溶液中形成的片段B-Fc接触，而接触2是晶体接触。
The model of human Fc fragment was refined at 2.9 .ANG. resolution. Two different automated procedures for crystallographic refinement were used. The final R value is 0.22. The dimer of CH3 domains closely resembles the CH1-CL aggregate in Fab fragments. There is no contact between CH2 domains. The contact between CH2 and CH3 domains has about 1/3 of the size of the CH3-CH3 contact. The carbohydrate, a branched chain of 9 hexose units, covers part of the C-contact face of the CH2 domain, shielding hydrophobic residues on this surface. Six atoms of the carbohydrate are within H-bonding distance of atoms in the CH2 domain. Crystallographic refinement of the complex between Fc fragment and fragment B of protein A from S. aureus reduced the R value of the model to 0.24. A major part of the structure of fragment B consists of 2 .alpha.-helices; the rest of the polypeptide chain is folded irregularly. In the crystal, fragment B forms 2 contacts with Fc fragment molecules. Contact 1 involves residues from both helices of fragment B, and residues from the CH2 and CH3 domains of Fc, and is predominantly hydrophobic. Contact 2 is smaller than contact 1. Residues from the 2nd helix and adjacent residues of fragment B and residues only from the CH3 domain of Fc contribute to contact 2. The nature of contact 2 is mainly polar and includes a sulfate ion. There are strong arguments that contact 1 is the fragment B-Fc contact formed in solution under physiological conditions, while contact 2 is a crystal contact.