Polarity/charge as a determinant of translocase requirements for membrane protein insertion
Polarity/charge as a determinant of translocase requirements for membrane protein insertion
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DOI：
10.1016/j.bbamem.2020.183502
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发表时间：
2021-02-01
影响因子：
3.4
通讯作者：
Dalbey, Ross E.
中科院分区：
文献类型：
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作者：
Hariharan, Balasubramani;Pross, Eva;Dalbey, Ross E.
大肠杆菌的YidC插入酶插入带有小质周环的膜蛋白（类似于20个残基）。然而，与带负电荷的残基相比，含有带正电荷残基的环很难运输，因此，与带负电荷的环相比，增加正电荷对Sec机制的要求更高（Zhu等人，2013；Soman等人，2014）。这表明膜蛋白质周区的极性和电荷决定了插入所需的YidC和Sec转位酶。在这里，我们通过证明即使在没有任何带电残基的情况下，当周质环转化为高极性时，我们的模型底物蛋白procoate - lep的插入也可以成为依赖于YidC/Sec的极性/电荷假设。此外，在高极性环中加入一些疏水氨基酸可以降低严格依赖sec的膜蛋白的sec依赖性。通过插入丙氨酸残基，我们也证明了原衣- lep环的长度确实是独立性的决定因素，而丙氨酸残基不会显著改变质周环的整体亲水性。综上所述，结果支持极性/电荷假设作为原衣插入转位酶要求的决定因素。
The YidC insertase of Escherichia coli inserts membrane proteins with small periplasmic loops (similar to 20 residues). However, it has difficulty transporting loops that contain positively charged residues compared to negatively charged residues and, as a result, increasing the positive charge has an increased requirement for the Sec machinery as compared to negatively charged loops (Zhu et al., 2013; Soman et al., 2014). This suggested that the polarity and charge of the periplasmic regions of membrane proteins determine the YidC and Sec translocase requirements for insertion. Here we tested this polarity/charge hypothesis by showing that insertion of our model substrate protein procoat-Lep can become YidC/Sec dependent when the periplasmic loop was converted to highly polar even in the absence of any charged residues. Moreover, adding a number of hydrophobic amino acids to a highly polar loop can decrease the Sec-dependence of the otherwise strictly Sec-dependent membrane proteins. We also demonstrate that the length of the procoat-Lep loop is indeed a determinant for Secdependence by inserting alanine residues that do not markedly change the overall hydrophilicity of the periplasmic loop. Taken together, the results support the polarity/charge hypothesis as a determinant for the translocase requirement for procoat insertion.