Sommer Nicole, Junne Tina, Kalies Kai-Uwe, Spiess Martin, Hartmann Enno
CSCM, Institute of Biology, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany.
Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
Biochim Biophys Acta. 2013 Dec;1833(12):3104-3111. doi: 10.1016/j.bbamcr.2013.08.018. Epub 2013 Sep 5.
Membrane protein insertion and topogenesis generally occur at the Sec61 translocon in the endoplasmic reticulum membrane. During this process, membrane spanning segments may adopt two distinct orientations with either their N- or C-terminus translocated into the ER lumen. While different topogenic determinants in membrane proteins, such as flanking charges, polypeptide folding, and hydrophobicity, have been identified, it is not well understood how the translocon and/or associated components decode them. Here we present evidence that the translocon-associated protein (TRAP) complex is involved in membrane protein topogenesis in vivo. Small interfering RNA (siRNA)-mediated silencing of the TRAP complex in HeLa cells enhanced the topology effect of mutating the flanking charges of a signal-anchor, but not of increasing signal hydrophobicity. The results suggest a role of the TRAP complex in moderating the 'positive-inside' rule.
膜蛋白插入和拓扑结构形成通常发生在内质网膜的Sec61转运体上。在此过程中，跨膜片段可能采取两种不同的取向，其N端或C端被转运到内质网腔中。虽然已经确定了膜蛋白中不同的拓扑决定因素，如侧翼电荷、多肽折叠和疏水性，但对于转运体和/或相关组分如何解读这些因素，人们还了解得不够深入。在这里，我们提供证据表明转运体相关蛋白（TRAP）复合物在体内参与膜蛋白拓扑结构形成。在HeLa细胞中，小干扰RNA（siRNA）介导的TRAP复合物沉默增强了突变信号锚侧翼电荷的拓扑效应，但没有增强增加信号疏水性的拓扑效应。结果表明TRAP复合物在调节“正内”规则中发挥作用。
