Roles of Carboxyl Groups in the Transmembrane Insertion of Peptides
Roles of Carboxyl Groups in the Transmembrane Insertion of Peptides
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DOI：
10.1016/j.jmb.2011.08.010
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发表时间：
2011-10-21
影响因子：
5.6
通讯作者：
Engelman, Donald M.
中科院分区：
文献类型：
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作者：
Barrera, Francisco N.;Weerakkody, Dhammika;Engelman, Donald M.
我们使用pHLIP (R) [pH（低）插入肽]来研究羧基在跨膜（TM）肽插入中的作用。在中性pH下，phillip以无序肽的形式与脂质双分子层表面结合；当pH值降低时，它穿过膜插入形成TM螺旋。当pH高于特征pK(a)（6.0）时，肽插入被逆转。促进膜插入的一个关键事件是天冬氨酸（Asp）和/或谷氨酸（Glu）残基的质子化，因为它们带负电荷的侧链阻碍了中性ph下的膜插入。为了获得机制理解，我们研究了一系列phillip变异体的膜插入和退出，其中四个Asp残基依次突变为非酸性残基，包括组氨酸（His）。我们的研究结果表明，在类似于ph4的情况下，由肽插入端羧基的质子化驱动，他的残基的存在并不能阻止pH依赖性肽膜插入。进一步的pH下降导致肽TM部分的His残基质子化，从而诱导肽从双分子层中退出。我们还发现，在膜插入过程中质子化变化的可电离残基的数量与ph依赖性插入脂质双分子层和退出脂质双分子层相关，并且协同性随着它们的数量增加而增加。我们期望我们的认识将被用于提高pHLIP对酸性病变组织的靶向性。(C) 2011 Elsevier Ltd.版权所有。
We have used pHLIP (R) [pH (low) insertion peptide] to study the roles of carboxyl groups in transmembrane (TM) peptide insertion. pHLIP binds to the surface of a lipid bilayer as a disordered peptide at neutral pH; when the pH is lowered, it inserts across the membrane to form a TM helix. Peptide insertion is reversed when the pH is raised above the characteristic pK(a) (6.0). A key event that facilitates membrane insertion is the protonation of aspartic acid (Asp) and/or glutamic acid (Glu) residues, since their negatively charged side chains hinder membrane insertion at neutral pH. In order to gain mechanistic understanding, we studied the membrane insertion and exit of a series of pHLIP variants where the four Asp residues were sequentially mutated to nonacidic residues, including histidine (His). Our results show that the presence of His residues does not prevent the pH-dependent peptide membrane insertion at similar to pH 4 driven by the protonation of carboxyl groups at the inserting end of the peptide. A further pH drop leads to the protonation of His residues in the TM part of the peptide, which induces peptide exit from the bilayer. We also find that the number of ionizable residues that undergo a change in protonation during membrane insertion correlates with the pH-dependent insertion into the lipid bilayer and exit from the lipid bilayer, and that cooperativity increases with their number. We expect that our understanding will be used to improve the targeting of acidic diseased tissue by pHLIP. (C) 2011 Elsevier Ltd. All rights reserved.