Kimbrough T G, Manoil C
Department of Genetics, University of Washington, Seattle 98195.
J Bacteriol. 1994 Nov;176(22):7118-20. doi: 10.1128/jb.176.22.7118-7120.1994.
The Escherichia coli serine chemoreceptor takes on a simple membrane topology with two transmembrane segments separating cytoplasmically disposed N and C termini from a central periplasmic domain. We investigated the role of the small N-terminal cytoplasmic domain in membrane insertion using alkaline phosphatase gene fusions. Mutations eliminating the positive charge of the domain altered insertion dramatically, with reciprocal effects on hybrids with periplasmic and C-terminal cytoplasmic fusion junctions. Efficient export of the normally cytoplasmic C-terminal domain required that, in addition to the N-terminal changes, a short amphiphatic sequence at the beginning of the C-terminal domain be also absent. These findings document the importance of the positive character of the N-terminal domain in chemoreceptor membrane insertion and imply that partially redundant sequence information controls the orientation of the second transmembrane segment.
大肠杆菌丝氨酸化学感受器具有简单的膜拓扑结构，两个跨膜区段将位于细胞质中的N端和C端与中央周质结构域分隔开来。我们利用碱性磷酸酶基因融合技术研究了小的N端细胞质结构域在膜插入中的作用。消除该结构域正电荷的突变显著改变了插入情况，对具有周质和C端细胞质融合连接点的杂合体产生了相反的影响。正常位于细胞质中的C端结构域的有效输出要求，除了N端的变化外，C端结构域起始处的一段短两性序列也不存在。这些发现证明了N端结构域的正性特征在化学感受器膜插入中的重要性，并暗示部分冗余的序列信息控制着第二个跨膜区段的方向。
