Wickner W
Proc Natl Acad Sci U S A. 1975 Dec;72(12):4749-53. doi: 10.1073/pnas.72.12.4749.
The coat protein of a filamentous phage (M13) enters the cytoplasmic membrane from two directions: from the outside upon infection and from the cell interior late in the viral life cycle prior to phage assembly and extrusion. Binding of 125I-labeled anti-coat protein antibody to spheroplasts or to inverted vesicles was used to assay the orientation of coat protein in the membrane. Both parental and newly synthesized coat protein were found to be exposed on the outer surface of the cytoplasmic membrane. Coat protein in intact infected cells is also accessible to external antibody. Thus two different processes of assembling a protein into membrane, each starting from a different membrane surface, appear to produce similar surface orientations.
丝状噬菌体（M13）的外壳蛋白从两个方向进入细胞质膜：感染时从外部进入，在病毒生命周期后期、噬菌体组装和挤出之前从细胞内部进入。用125I标记的抗外壳蛋白抗体与原生质球或反向囊泡结合来测定外壳蛋白在膜中的方向。发现亲本和新合成的外壳蛋白都暴露在细胞质膜的外表面。完整感染细胞中的外壳蛋白也能与外部抗体结合。因此，将一种蛋白质组装到膜中的两种不同过程，每种过程都从不同的膜表面开始，似乎产生了相似的表面方向。
