α-2-巨球蛋白
化学
巨球蛋白
阿尔法(金融)
联想(心理学)
细胞因子
生物物理学
生物化学
生物
免疫学
医学
心理学
结构效度
护理部
患者满意度
心理治疗师
作者
Kendall P. Crookston,Donna J. Webb,Beni B. Wolf,Steven L. Gonias
标识
DOI:10.1016/s0021-9258(17)42289-7
摘要
alpha 2-Macroglobulin (alpha 2M) binds numerous cytokines; however, since binding affinities have not been determined, it is difficult to compare various alpha 2M-cytokine interactions or predict whether alpha 2M-cytokine complexes will form in the presence of other cytokine-binding macromolecules. In this investigation, we used a novel method to demonstrate that transforming growth factor-beta 1 (TGF-beta 1), TGF-beta 2, nerve growth factor-beta (NGF-beta), platelet derived growth factor-BB (PDGF-BB), tumor necrosis factor-alpha (TNF-alpha), and basic fibroblast growth factor (bFGF) reversibly associate with alpha 2M-methylamine to form noncovalent complexes. Apparent equilibrium was achieved in less than 15 min. Noncovalent alpha 2M-cytokine complexes were converted into covalent complexes; however, this occurred slowly. Therefore, a rapid equilibrium assumption was applied and equilibrium dissociation constants were determined using a single binding site model. KD values for the binding of cytokines to alpha 2M-methylamine varied by 2 orders of magnitude. The rank order of affinity was TGF-beta 2 (13 +/- 2 nM) > TGF-beta 1, NGF-beta > PDGF-BB > or = bFGF > TNF-alpha. Native alpha 2M bound TGF-beta 1, TGF-beta 2, NGF-beta, PDGF-BB, and TNF-alpha. Interferon-gamma did not bind to native alpha 2M or alpha 2M-methylamine. Each cytokine bound native alpha 2M with lower affinity than alpha 2M-methylamine except for TGF-beta 2 which bound both forms with equal affinity. In non-equilibrium systems, alpha 2M-methylamine appeared to bind more TGF-beta 2 due to the more rapid dissociation of TGF-beta 2-native alpha 2M complex. The classification of alpha 2M-cytokine complexes according to binding affinity should predict which complexes are most likely to form in cell culture and under various conditions in vivo.
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