Department of Biology, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
Biochemistry. 2010 Mar 23;49(11):2359-67. doi: 10.1021/bi1000933.
Naturally occurring genetic variability across HIV-1 subtypes causes amino acid polymorphisms in encoded HIV-1 proteins including the envelope glycoproteins associated with viral entry. The effects of amino acid polymorphisms on the mechanism of HIV-1 entry into cells, a process initiated by the binding of the viral envelope glycoprotein gp120 to the cellular CD4 receptor, are largely unknown. In this study, we demonstrate that amino acid polymorphisms affect the structural stability and domain cooperativity of gp120 and that those differences are reflected in the binding mechanism of the viral envelope glycoprotein to the cell surface receptor and coreceptor. Moreover, subtype differences also affect the binding behavior of experimental HIV cell entry inhibitors. While gp120-A has a slightly lower denaturation temperature than gp120-B, the most notable stability difference is that for gp120-B the van't Hoff to calorimetric enthalpy ratio (DeltaH(vH)/DeltaH) is 0.95 whereas for gp120-A is 0.6, indicative of more cooperative domain/domain interactions in gp120-B, as this protein more closely approaches a two-state transition. Isothermal titration calorimetry demonstrates that CD4 and 17b (a surrogate antibody for the chemokine coreceptor) exhibit 7- and 3-fold weaker binding affinities for gp120-A. The binding of these proteins as well as that of the experimental entry inhibitor NBD-556 induces smaller conformational changes in gp120-A as evidenced by significantly smaller binding enthalpies and binding entropies. Together, these results describe the effects of gp120 polymorphisms on binding to host cell receptors and emphasize that guidelines for developing future entry inhibitors must recognize and deal with genomic differences between HIV strains.
HIV-1 各亚型之间天然存在的遗传变异性导致编码 HIV-1 蛋白的氨基酸发生多态性，其中包括与病毒进入相关的包膜糖蛋白。氨基酸多态性对 HIV-1 进入细胞的机制的影响尚不清楚，该过程是由病毒包膜糖蛋白 gp120 与细胞表面 CD4 受体结合引发的。在这项研究中，我们证明了氨基酸多态性会影响 gp120 的结构稳定性和结构域协同性，这些差异反映在病毒包膜糖蛋白与细胞表面受体和共受体的结合机制中。此外，亚型差异也会影响实验性 HIV 细胞进入抑制剂的结合行为。虽然 gp120-A 的变性温度略低于 gp120-B，但最显著的稳定性差异是，对于 gp120-B，van't Hoff 到量热焓比（DeltaH(vH)/DeltaH）为 0.95，而对于 gp120-A 为 0.6，这表明 gp120-B 中结构域/结构域相互作用更具协同性，因为该蛋白更接近二态转变。等温滴定量热法表明，CD4 和 17b（趋化因子共受体的替代抗体）与 gp120-A 的结合亲和力分别弱 7 倍和 3 倍。这些蛋白的结合以及实验性进入抑制剂 NBD-556 的结合会引起 gp120-A 发生较小的构象变化，这可以从较小的结合焓和结合熵得到证明。综上所述，这些结果描述了 gp120 多态性对与宿主细胞受体结合的影响，并强调了开发未来进入抑制剂的指南必须认识到并处理 HIV 株之间的基因组差异。
