Dual topology of the processed hepatitis C virus protein NS4B is influenced by the NS5A protein
Dual topology of the processed hepatitis C virus protein NS4B is influenced by the NS5A protein
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DOI：
10.1099/vir.0.82211-0
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发表时间：
2006-11-01
影响因子：
3.8
通讯作者：
Persson, Mats A. A.
中科院分区：
文献类型：
--
作者：
Lundin, Marika;Lindstrom, Hannah;Persson, Mats A. A.
丙型肝炎病毒的非结构蛋白4 B（NS 4 B）是最不为人所知的蛋白。它定位于内质网（ER）膜并诱导膜变化，导致膜网，据报道是病毒复制的场所。先前提出了基于体外数据的重组HCV NS 4 B的Ia基因型的拓扑结构的模型。在该模型中，相当一部分NS 4 B分子的N-末端尾部通过翻译后过程易位到ER腔中，使蛋白质具有双跨膜拓扑结构。现在报道，在多蛋白的背景下，在细胞中表达的加工的NS 4 B也发生N末端的易位。然而，在NS 5A的存在下，观察到较低程度的易位，这可能表明NS 5A影响NS 4 B的拓扑结构。来自所有主要基因型的NS 4 B的体外表达研究表明，N末端易位到ER腔在基因型间是保守的。这清楚地表明了该功能的重要功能。此外，当破坏先前报道的NS 4 B的N末端的两亲性螺旋（AH）时，易位被抑制。由于破坏的AH也废除了NS 4 B重排膜的能力，这些数据首次表明N末端易位和膜重排之间的关联。最后，本实验还证实了第一管腔环的预测位置在aa 112周围。
Among the least-known hepatitis C virus proteins is the non-structural protein 4B (NS4B). It localizes to the endoplasmic reticulum (ER) membrane and induces membrane changes, resulting in a membranous web that is reported to be the locale for virus replication. A model was presented previously for the topology of recombinant HCV NS4B of the 1 a genotype based on in vitro data. In this model, the N-terminal tail of a considerable fraction of the NS4B molecules was translocated into the ER lumen via a post-translational process, giving the protein a dual transmembrane topology. It is now reported that translocation of the N terminus also occurs for processed NS4B expressed in cells in the context of the polyprotein. In the presence of NS5A, however, a lower degree of translocation was observed, which may indicate that NS5A influences the topology of NS4B. In vitro expression studies of NS4B from all major genotypes demonstrated that translocation of the N terminus to the ER lumen is conserved across genotypes. This clearly suggests an important function for this feature. Furthermore, when disrupting a previously reported amphipathic helix (AH) in the N terminus of NS4B, translocation was inhibited. As a disrupted AH also abolished the ability of NS4B to rearrange membranes, these data indicate for the first time an association between translocation of the N terminus and membrane rearrangement. Finally, the present experiments also confirm the predicted location of the first luminal loop to be around aa 112.