INTERACTION OF BETA-1H GLOBULIN WITH CELL-BOUND C3B - QUANTITATIVE-ANALYSIS OF BINDING AND INFLUENCE OF ALTERNATIVE PATHWAY COMPONENTS ON BINDING
INTERACTION OF BETA-1H GLOBULIN WITH CELL-BOUND C3B - QUANTITATIVE-ANALYSIS OF BINDING AND INFLUENCE OF ALTERNATIVE PATHWAY COMPONENTS ON BINDING
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DOI：
10.1084/jem.147.6.1792
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发表时间：
1978-01-01
影响因子：
15.3
通讯作者：
RUDDY, S
中科院分区：
文献类型：
--
作者：
CONRAD, DH;CARLO, JR;RUDDY, S
通过免疫荧光和放射性示踪技术显示纯化的β 1 H球蛋白（β 1 H）与C3 B [补体成分3的B片段]包被的细胞结合。对于EAC 43 [红细胞，抗体，C43复合物]，结合的β 1H的量与用于制备细胞的C3的量成正比; EA、EAC 14和EAC 14 oxy 2结合非常少量的β 1H。β 1H上的C3 b结合位点是不稳定的，因为即使存在过量的细胞结合的C3 b，也不是所有纯化的125 I-β 1H都能够结合C3 b。β 1H与C3 b包被细胞结合的Scatchard分析表明平衡常数为109 L/M。在Scatchard分析中经常发现线性偏差。β 1H结合位点表现出负协同性，因为随着更多位点被占据，填充剩余位点变得更加困难。使用用131 I-C3和用125 I标记的β 1H制备的EAC 14 oxy 23检查C3 b和β 1H之间反应的化学计量。每个C3 b分子结合0.5-0.8个β 1H分子。旁路途径组分影响125 I-β 1H与细胞结合的C3 b的结合。C3 b和天然C3均以未标记β 1H的约1/1，000的效率抑制标记β 1H的结合。因子B以未标记的β 1H的1/280的效率抑制结合。备解素[P]引起β 1H结合的剂量依赖性增加;如果反应混合物中还存在B，则这种增强被消除。Scatchard分析表明，P对β 1H结合的增强导致可用结合位点数目的增加，而不是结合亲和力的增加。
Purified .beta.1H globulin (.beta.1H) was shown to bind to C3b [b fragment of complement component 3] coated cells by immunofluorescent and radioactive tracer techniques. With EAC43 [erythrocyte, antibody, C43 complex], the amount of .beta.1H bound was directly proportional to the amount of C3 used to prepare the cells; EA, EAC14 and EAC14oxy2 bound very small amounts of .beta.1H. The C3b binding site on .beta.1H was labile in that not all of the purified 125I-.beta.1H was capable of binding to C3b, even when an excess of cell-bound C3b was present. Scatchard analysis of binding of .beta.1H to C3b-coated cells indicated an equilibrium constant of 109 L/M. Deviations from linearity were regularly found on Scatchard analyses. The .beta.1H binding sites exhibit negative cooperativity in that as more sites become occupied, it becomes more difficult to fill the remaining sites. The stoichiometry of the reaction between C3b and .beta.1H was examined using EAC14oxy23 prepared with 131I-C3 and .beta.1H labeled with 125I. Between 0.5-0.8 .beta.1H molecules were bound per C3b molecule. Alternative pathway components influenced the binding of 125I-.beta.1H to cell bound C3b. Both C3b and native C3 inhibited binding of labeled .beta.1H at an efficiency approximately 1/1,000 that of unlabeled .beta.1H. Factor B inhibited binding with 1/280 the efficiency of unlabeled .beta.1H. Properdin [P] caused a dose-dependent increase in the binding of .beta.1H; this enhancement was abrogated if B was also present in the reaction mixture. Scatchard analysis indicated that the enhancement of .beta.1H binding by P resulted in an increased number of available binding sites rather than an increase in the affinity of binding.