Protein Arp and protein H from group A streptococci. Ig binding and dimerization are regulated by temperature.
Protein Arp and protein H from group A streptococci. Ig binding and dimerization are regulated by temperature.
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来自 A 组链球菌的蛋白 Arp 和蛋白 H。
DOI：
10.4049/jimmunol.148.10.3238
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发表时间：
1992
影响因子：
4.4
通讯作者：
A. Lindqvist
中科院分区：
文献类型：
--
作者：
B. Åkerström;G. Lindahl;L. Björck;A. Lindqvist
与IG的Fc部分结合的细胞表面蛋白由A组链球菌（一种重要的人类病原体）的许多菌株表达。两种这样的细菌菌株，AP 4和AP 1，显示出以温度依赖性的方式分别结合伊加和IgG。放射性标记的IG与细菌细胞的结合在37 ℃时低于22 ℃和4 ℃时。类似地，蛋白质阿普（分离自菌株AP 4的IgA结合蛋白）和蛋白质H（分离自菌株AP 1的IgG结合蛋白）在22 ℃和较低温度下显示出强的Ig结合，而在37 ℃下几乎完全不结合。这种效应是可逆的：降低温度可以恢复结合，反之亦然。在27至37摄氏度之间，结合和非结合之间发生了逐渐的转变。凝胶层析和速度沉降离心表明，蛋白质阿普和蛋白质H在10和22 ℃下以非共价缔合的二聚体出现，在37 ℃下以单体出现。这些结果强烈表明，蛋白质阿普和蛋白质H的二聚化，而不是低温本身，在10和22 ℃下产生了蛋白质的强Ig结合。事实上，在10 ℃下通过与低浓度戊二醛孵育使二聚体共价交联后，甚至在37 ℃下也实现了完全的Ig结合。蛋白质阿普的羧基末端蛋白水解片段在任何温度下都完全缺乏IgA结合能力，显示出与完整蛋白质阿普相同的温度依赖性二聚化，这表明蛋白质的Ig结合部分不需要二聚化。这些结果的Ig结合A族链球菌蛋白的功能的影响，及其在宿主-寄生虫关系中的作用进行了讨论。
Cell surface proteins that bind to the Fc part of Ig are expressed by many strains of group A streptococci, an important human pathogen. Two such bacterial strains, AP4 and AP1, were shown to bind IgA and IgG, respectively, in a temperature-dependent manner. The binding of radiolabeled Ig to the bacterial cells was lower at 37 degrees C than at 22 and 4 degrees C. Similarly, protein Arp, the IgA-binding protein isolated from strain AP4, and protein H, the IgG-binding protein isolated from strain AP1, displayed a strong Ig-binding at 22 degrees C and lower temperatures, and virtually no binding at all at 37 degrees C. The effect was reversible: lowering of the temperature restored the binding and vice versa. A gradual shift between binding and nonbinding took place between 27 and 37 degrees C. Gel chromatography and velocity sedimentation centrifugation showed that protein Arp and protein H appeared as noncovalently associated dimers at 10 and 22 degrees C, and as monomers at 37 degrees C. These results strongly suggest that the dimerization of protein Arp and protein H, rather than the low temperature itself, yielded the strong Ig-binding of the proteins at 10 and 22 degrees C. Indeed, after covalent cross-linking of the dimers at 10 degrees C by incubation with low concentrations of glutaraldehyde, full Ig-binding was achieved even at 37 degrees C. A carboxyl-terminal proteolytic fragment of protein Arp, which completely lacked the IgA-binding capacity at any temperature, showed the same temperature-dependent dimerization as intact protein Arp, suggesting that the Ig-binding part of the protein is not required for dimerization. The implications of these results for the function of Ig-binding group A streptococcal proteins, and their role in the host-parasite relationship are discussed.