3-DIMENSIONAL SOLUTION STRUCTURE OF THE B-DOMAIN OF STAPHYLOCOCCAL PROTEIN-A - COMPARISONS OF THE SOLUTION AND CRYSTAL-STRUCTURES
3-DIMENSIONAL SOLUTION STRUCTURE OF THE B-DOMAIN OF STAPHYLOCOCCAL PROTEIN-A - COMPARISONS OF THE SOLUTION AND CRYSTAL-STRUCTURES
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DOI：
10.1021/bi00155a020
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发表时间：
1992-10-13
期刊：
影响因子：
2.9
通讯作者：
SHIMADA, I
中科院分区：
文献类型：
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作者：
GOUDA, H;TORIGOE, H;SHIMADA, I
利用核磁共振波谱和混合距离几何-动力学模拟退火计算确定了葡萄球菌A蛋白重组体B结构域（FB）的三维溶液结构。基于692个实验约束，包括587个由核Overhauser效应（NOE）得到的距离约束、57个扭转角（phi，chi 1）约束和48个与24个氢键相关的约束，得到了FB的10个收敛结构. 10个聚合结构之间的原子均方根差对于骨架原子为0.52 +/-0.10埃，对于所有重原子为0.98 +/-0.08埃（不包括从Thr 1到Glu 9的N-末端片段和从Gln 56到Ala 60的C-末端片段，它们是部分无序的）。FB由一束三个α-螺旋组成，即，螺旋I（Gln 10-His 19）、螺旋II（Glu 25-Asp 37）和螺旋III（Ser 42-Ala 55）。阻碍II和螺旋III彼此反平行，而螺旋I的长轴相对于螺旋II和螺旋III的长轴以约30度的角度倾斜。FB的大部分疏水残基被埋在三个螺旋束的内部。这表明，掩埋的疏水残基形成疏水核心，有助于FB的稳定性。通过观察H-N-15 NMR谱进行酰胺质子交换实验的结果的基础上，我们得出结论，在溶液中的Fc FB复合物中保留了三个螺旋的束的结构。这一结果与Fc-FB复合物的X射线晶体学研究[Deisenhofer，J.（1981）Biochemistry 20，2361-2370]的结果形成鲜明对比，后者显示Ser 42-Glu 48片段被延长，并且没有关于Ala 49-Lys 59片段的结构信息。我们认为，在Fc结合FB的晶体接触是负责在晶体中的Ser 42-Ala 55段的无序结构。
The three-dimensional solution structure of the recombinant B domain (FB) of staphylococcal protein A, which specifically binds to the Fc portion of immunoglobulin G, was determined by NMR spectroscopy and hybrid distance geometry-dynamical simulated annealing calculations. On the basis of 692 experimental constraints including 587 distance constraints obtained from the nuclear Overhauser effect (NOE), 57 torsion angle (phi, chi1) constraints, and 48 constraints associated with 24 hydrogen bonds, a total of 10 converged structures of FB were obtained. The atomic root mean square difference among the 10 converged structures is 0.52 +/- 0.10 angstrom for the backbone atoms and 0.98 +/- 0.08 angstrom for all heavy atoms (excluding the N-terminal segment from Thr1 to Glu9 and the C-terminal segment from Gln56 to Ala60, which are partially disordered). FB is composed of a bundle of three alpha-helices, i.e., helix I (Gln10-His19), helix II (Glu25-Asp37), and helix III (Ser42-Ala55). Helix II and helix III are antiparallel to each other, whereas the long axis of helix I is tilted at an angle of about 30-degrees with respect to those of helix II and helix III. Most of the hydrophobic residues of FB are buried in the interior of the bundle of the three helices. It is suggested that the buried hydrophobic residues form a hydrophobic core, contributing to the stability of FB. On the basis of the results of amide proton exchange experiments performed by observing heteronuclear H-1-N-15 NMR spectra, we have concluded that the structure of the bundle of the three helices is retained in the Fc-FB complex in solution. This result is in marked contrast to that of an X-ray crystallographic study of the Fc-FB complex [Deisenhofer, J. (1981) Biochemistry 20, 2361-2370], which shows that the Ser42-Glu48 segment is extended and no structural information is available on the Ala49-Lys59 segment. We suggest that crystal contact in the Fc-bound FB is responsible for the disordered structure of the Ser42-Ala55 segment in the crystal.