Bovine leukemia virus SU protein interacts with zinc, and mutations within two interacting regions differentially affect viral fusion and infectivity in vivo
Bovine leukemia virus SU protein interacts with zinc, and mutations within two interacting regions differentially affect viral fusion and infectivity in vivo
复制标题
DOI：
10.1128/jvi.76.16.7956-7967.2002
复制
发表时间：
2002-08-01
影响因子：
5.4
通讯作者：
Kettmann, R
中科院分区：
文献类型：
--
作者：
Gatot, JS;Callebaut, I;Kettmann, R
牛白血病病毒（BLV）和人嗜T淋巴细胞病毒I型（HTLV-1）属于δ逆转录病毒属。它们进入宿主细胞被认为是通过细胞外（SU）包膜糖蛋白与细胞受体的相互作用介导的。为了深入了解这一过程的机制，我们研究了SU蛋白与特定配体相互作用的能力。特别是，通过亲和层析，我们已经表明，BLV SU蛋白特异性地与锌离子相互作用。为了鉴定参与结合的蛋白质结构域，测试了沿着序列分布的16种肽。其中两种似乎能够与锌相互作用。为了阐明这些SU区域在病毒生物学中的作用，将突变引入BLV分子克隆的env基因中，以修饰可能与锌相互作用的残基。在第一锌结合区（104至123）内突变的包膜的融合能力被完全消除。此外，该结构域的完整性也是体内感染性所必需的。相比之下，第二个锌结合区（218到237）内的突变并不妨碍融合能力;事实上，合胞体甚至更大。在绵羊中，区域218至237的突变没有改变感染性或病毒传播。最后，我们证明了相关HTLV-1的包膜也能够结合锌。有趣的是，发现锌离子与Friend鼠白血病病毒（Fr-MLV）SU糖蛋白的受体结合结构域（RBD）相关，进一步支持它们在SU结构中的相关性。基于与Fr-MLV RBD共享的序列相似性，其三维结构已通过实验确定，我们将BLV锌结合肽104 - 123定位在潜在受体结合表面的相对侧。这一观察结果支持了以下假设：锌离子可以介导SU RBD与SU的C-末端部分的相互作用，从而有助于SU结构完整性，或者与不同于受体的伴侣相互作用。
Bovine leukemia virus (BLV) and human T-cell lymphotropic virus type I (HTLV-1) belong to the genus of deltaretroviruses. Their entry into the host cell is supposed to be mediated by interactions of the extracellular (SU) envelope glycoproteins with cellular receptors. To gain insight into the mechanisms governing this process, we investigated the ability of SU proteins to interact with specific ligands. In particular, by affinity chromatography, we have shown that BLV SU protein specifically interacted with zinc ions. To identify the protein domains involved in binding, 16 peptides distributed along the sequence were tested. Two of them appeared to be able to interact with zinc. To unravel the role of these SU regions in the biology of the virus, mutations were introduced into the env gene of a BLV molecular clone in order to modify residues potentially interacting with zinc. The fusogenic capacity of envelope mutated within the first zinc-binding region (104 to 123) was completely abolished. Furthermore, the integrity of this domain was also required for in vivo infectivity. In contrast, mutations within the second zinc-binding region (218 to 237) did not hamper the fusogenic capacity; indeed, the syncytia were even larger. In sheep, mutations in region 218 to 237 did not alter infectivity or viral spread. Finally, we demonstrated that the envelope of the related HTLV-1 was also able to bind zinc. Interestingly, zinc ions were found to be associated with the receptor-binding domain (RBD) of Friend murine leukemia virus (Fr-MLV) SU glycoprotein, further supporting their relevance in SU structure. Based on the sequence similarities shared with the Fr-MLV RBD, whose three-dimensional structure has been experimentally determined, we located the BLV zinc-binding peptide 104-123 on the opposite side of the potential receptor-binding surface. This observation supports the hypothesis that zinc ions could mediate interactions of the SU RBD either with the C-terminal part of SU, thereby contributing to the SU structural integrity, or with a partner(s) different from the receptor.