Ota K, Sakaguchi M, von Heijne G, Hamasaki N, Mihara K
Department of Molecular Biology, Graduate School of Medical Science, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Mol Cell. 1998 Oct;2(4):495-503. doi: 10.1016/s1097-2765(00)80149-5.
In a current model of integration of multispanning membrane proteins into the endoplasmic reticulum, it is proposed that the transmembrane segments show alternating translocation initiation and stop-transfer functions. Here, we present evidence for a mode of cotranslational insertion in which an internal signal-anchor sequence with Nexo/Ccyt topology confers a transmembrane disposition onto a preceding hydrophilic segment, resulting in a topology where the hydrophilic segment apparently can slip back and forth across the membrane. Our results demonstrate that hydrophobicity is not, as hitherto thought, an absolute requirement for the formation of a transmembrane segment, and suggest that integral membrane proteins may contain hydrophilic transmembrane segments with a considerable freedom to move in relation to the membrane.
在当前多跨膜蛋白整合到内质网的模型中，有人提出跨膜片段具有交替的易位起始和停止转移功能。在此，我们提供了一种共翻译插入模式的证据，即具有Nexo/Ccyt拓扑结构的内部信号锚定序列赋予前一个亲水片段跨膜定位，导致一种拓扑结构，其中亲水片段显然可以在膜上来回滑动。我们的结果表明，疏水性并非如迄今所认为的那样是形成跨膜片段的绝对必要条件，并表明整合膜蛋白可能包含相对于膜具有相当大移动自由度的亲水跨膜片段。
