Rudolf Virchow Center, Center for Integrative and Translational Bioimaging, University of Würzburg, 97080 Würzburg, Germany.
Biocenter, University of Würzburg, 97074 Würzburg, Germany.
Viruses. 2021 Oct 20;13(11):2115. doi: 10.3390/v13112115.
(1) Background: During maturation of the Hepatitis B virus, a viral polymerase inside the capsid transcribes a pre-genomic RNA into a partly double stranded DNA-genome. This is followed by envelopment with surface proteins inserted into a membrane. Envelopment is hypothetically regulated by a structural signal that reports the maturation state of the genome. NMR data suggest that such a signal can be mimicked by the binding of the detergent Triton X 100 to hydrophobic pockets in the capsid spikes. (2) Methods: We have used electron cryo-microscopy and image processing to elucidate the structural changes that are concomitant with the binding of Triton X 100. (3) Results: Our maps show that Triton X 100 binds with its hydrophobic head group inside the pocket. The hydrophilic tail delineates the outside of the spike and is coordinated via Lys-96. The binding of Triton X 100 changes the rotamer conformation of Phe-97 in helix 4, which enables a π-stacking interaction with Trp-62 in helix 3. Similar changes occur in mutants with low secretion phenotypes (P5T and L60V) and in a mutant with a pre-mature secretion phenotype (F97L). (4) Conclusion: Binding of Triton X 100 is unlikely to mimic structural maturation because mutants with different secretion phenotypes show similar structural responses.
（1）背景：在乙型肝炎病毒成熟过程中，衣壳内的病毒聚合酶将前基因组 RNA 转录成部分双链 DNA 基因组。随后，表面蛋白插入到包膜中。包膜理论上受报告基因组成熟状态的结构信号调控。NMR 数据表明，这种信号可以通过去污剂 Triton X 100 与衣壳刺突中的疏水性口袋结合来模拟。（2）方法：我们使用电子冷冻显微镜和图像处理来阐明与 Triton X 100 结合相伴的结构变化。（3）结果：我们的图谱显示，Triton X 100 带有其疏水性头部基团在口袋内结合。亲水性尾巴描绘了刺突的外部，并通过 Lys-96 进行协调。Triton X 100 的结合改变了 Phe-97 在 4 号螺旋中的旋转构象，使其能够与 3 号螺旋中的 Trp-62 发生 π-堆积相互作用。具有低分泌表型的突变体（P5T 和 L60V）和具有早熟分泌表型的突变体（F97L）都发生了类似的变化。（4）结论：Triton X 100 的结合不太可能模拟结构成熟，因为具有不同分泌表型的突变体显示出相似的结构反应。
