Morrison T G, Peeples M E, McGinnes L W
Proc Natl Acad Sci U S A. 1987 Feb;84(4):1020-4. doi: 10.1073/pnas.84.4.1020.
The fusion glycoprotein of Newcastle disease virus is synthesized as an inactive precursor, F0. During intracellular transport and maturation, F0 undergoes a conformational change resulting from the loss of intramolecular disulfide bonds. F0 is also cleaved to yield F1, F2, the active, membrane-fusing form of the protein. Two monoclonal antibodies were used to explore this conformational change and its relationship to cleavage. These antibodies failed to precipitate the pulse-labeled fusion protein but did precipitate the F0 and the F1, F2 forms of the "chase" fusion protein. Use of the inhibitors carbonylcyanide m-chlorophenylhydrazone and monensin showed that the fusion protein acquired the ability to react with the monoclonal antibodies after it left the rough endoplasmic reticulum but before it left the medial Golgi membranes and before it was cleaved. The acquisition of antigenicity correlates with the disruption of intramolecular disulfide bonds during transit through the cell. This correlation was directly confirmed. The pulse-labeled fusion protein could be recognized by both monoclonal antibodies if the protein was first reduced. The formation and disruption of intramolecular disulfide bonds as a posttranslational modification of glycoproteins is discussed.
新城疫病毒的融合糖蛋白最初以无活性的前体F0形式合成。在细胞内运输和成熟过程中，F0由于分子内二硫键的丢失而发生构象变化。F0还会被切割产生F1和F2，即该蛋白的具有膜融合活性的形式。使用两种单克隆抗体来探究这种构象变化及其与切割的关系。这些抗体无法沉淀脉冲标记的融合蛋白，但能沉淀“追踪”融合蛋白的F0以及F1、F2形式。使用抑制剂羰基氰化物间氯苯腙和莫能菌素表明，融合蛋白在离开糙面内质网后但在离开高尔基体中间膜之前且在被切割之前获得了与单克隆抗体反应的能力。抗原性的获得与在细胞内转运过程中分子内二硫键的断裂相关。这种相关性得到了直接证实。如果首先对脉冲标记的融合蛋白进行还原，它就能被两种单克隆抗体识别。本文讨论了作为糖蛋白翻译后修饰的分子内二硫键的形成和断裂。
