Structural study of the HIV1 gp41 coat protein

截断gp41结构刚刚超过其跨膜结构域，留下1-190个残基，得到结构良好的蛋白质，可溶于十二烷基麦芽糖苷，同时采用其天然的同源三聚体形式。蛋白质被发现非常稳定，即使在50摄氏度的温度下也是如此，并且样品被发现适合于核磁共振波谱。初步分析表明，即使胞外结构域共振被严重加宽，具有慢分子翻滚的特点，三聚体的融合结构域仍能产生良好的核磁共振波谱特征。我们发现这些融合结构域的化学位移与先前在十二烷基硫酸钠胶束中研究的孤立结构域的化学位移非常接近，并发现它们是均匀的α-螺旋结构。融合结构域的有效关联时间比大的三聚体复合体的其余部分要短得多，这表明完整的融合结构域螺旋在洗涤剂胶束中高度移动，同时保持其螺旋构象。这排除了先前假设的与gp41跨膜结构域的相互作用。

Truncation of the gp41 construct just past its transmembrane domain, leaving residues 1-190, results in a well-structured protein, soluble in dodecylmaltoside while adopting its natural homo-trimeric form. The protein is found to be quite stable, even at temperatures of 50C, and samples are found to be suitable for NMR spectroscopy. Preliminary analysis shows that even thought the ecto-domain resonances are severely broadened, characteristic of slow molecular tumbling, the fusion domains of the trimer yield good NMR spectral characteristics. We find that these fusion domains exhibit chemical shifts that fall very close to those of the isolated domain, previously studied in SDS micelles and found to be uniformly alpha-helical. The fusion domains exhibit effective correlation times that are much shorter than for the remainder of the large trimeric complex, indicating that the intact fusion domain helices are highly mobile within the detergent micelle, while retaining their helical conformation. This excludes the previously hypothesized interaction with the gp41 transmembrane domain.