HIV-1 capsid is comprised of over a hundred p24 protein molecules, arranged as either pentamers or hexamers. Three p24 mutants with amino acid substitutions in capsid N-terminal domain protein were examined: G60W (α3-4 loop), M68T (helix 4), and P90T (α4-5 loop), which exhibited no viability for biological activity. One common structural feature of the three p24 N-domain mutants, examined by NMR, was the long-range effect of more β-structures at the β2-strand in the N-terminal region compared with the wild-type. In addition, the presence of fewer helical structures was observed in M68T and P90T, beyond the broad area from helix 1 to the C-terminal part of helix 4. This suggests that both N-terminal beta structures and helices play important roles in the formation of p24 hexamers and pentamers. Next, compared with P90T, we examined cis-conformation or trans-conformation of wild-type adopted by isomerization at G89–P90. Since P90T mutant adopts only a trans-conformation, comparison of chemical shifts and signal intensities between each spectra revealed that the major peaks (about 85%) in the spectrum of wild-type correspond to trans-conformation. Furthermore, it was indicated that the region in cis-conformation (minor; 15%) was more stabilized than that observed in trans-conformation, based on the analyses of heteronuclear Overhauser effect as well as the order-parameter. Therefore, it was concluded that the cis-conformation is more favorable than the trans-conformation for the interaction between the p24 N-terminal domain and cyclophilin-A. This is because HIV-1 with a P90T protein, which adopts only a trans-conformation, is associated with non-viability of biological activity.

中文翻译：

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由氨基酸取代引起的 HIV-1 p24 衣壳蛋白 N 域动态和静态结构的变化与其病毒活力有关

HIV-1 衣壳由一百多个 p24 蛋白分子组成，排列为五聚体或六聚体。检测了三个在衣壳 N 端结构域蛋白中具有氨基酸取代的 p24 突变体：G60W（α3-4 环）、M68T（螺旋 4）和 P90T（α4-5 环），它们没有表现出生物活性。三个 p24 N 结构域突变体的一个共同结构特征，通过 NMR 检测，与野生型相比，在 N 末端区域的 β2 链上存在更多 β 结构的长程效应。此外，在从螺旋 1 到螺旋 4 的 C 末端部分的广阔区域之外，在 M68T 和 P90T 中观察到较少螺旋结构的存在。这表明 N 末端 β 结构和螺旋在形成中都起重要作用p24 六聚体和五聚体。接下来，与 P90T 相比，我们考察了在 G89-P90 异构化采用的野生型的顺式构象或反式构象。由于P90T突变体仅采用反式构象，比较各光谱之间的化学位移和信号强度表明，野生型光谱中的主要峰（约85％）对应于反式构象。此外，基于异核 Overhauser 效应和序参数的分析表明，顺式构象区域（次要；15%）比反式构象区域更稳定。因此，得出的结论是顺式构象比反式构象更有利-p24 N-末端结构域和亲环蛋白-A之间相互作用的构象。这是因为带有仅采用反式构象的 P90T 蛋白的 HIV-1 与生物活性的非活力有关。