Membrane Protein Crystallization in Lipidic Mesophases. Hosting Lipid Effects on the Crystallization and Structure of a Transmembrane Peptide
Membrane Protein Crystallization in Lipidic Mesophases. Hosting Lipid Effects on the Crystallization and Structure of a Transmembrane Peptide
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DOI：
10.1021/cg101384p
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发表时间：
2011-04-01
影响因子：
3.8
通讯作者：
Caffrey, Martin
中科院分区：
文献类型：
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作者：
Hoefer, Nicole;Aragao, David;Caffrey, Martin
革兰西菌素是一种由D-和l -氨基酸交替组成的极性五肽抗生素。在某种程度上，它的作用是在敏感细胞的膜上制造孔，使它们向单价阳离子泄漏。肽应该能够以双链缠绕双螺旋结构（DSDH）或头对头单链螺旋结构（HHSH）穿过宿主膜。目前的结构模型是基于大分子x射线晶体学（MX）和核磁共振（NMR）。然而，HHSH的形式只被核磁共振观察到。不同的革兰杀菌素构象的形状和大小不同。因此，我们推测，将其重组为具有不同微观结构的双层的脂质中间相将优先稳定一种形式。通过使用这些中间相进行中介晶生成，期望至少有一种中间相可以生成HHSH形式的革兰杀菌素晶体，以供MX测定结构。这是测试使用商业和内部合成的脂质，支持介晶形成。脂质酰基链长度从14到18个碳不等，以提供具有一定双层厚度的中间相。出乎意料的是，所有脂质都产生了高质量的结构级晶体，其中革兰杀菌素仅具有DSDH构象。
Gramicidin is an apolar pentadecapeptide antibiotic consisting of alternating D- and L-amino acids. It functions, in part, by creating pores in membranes of susceptible cells rendering them leaky to monovalent cations. The peptide should be able to traverse the host membrane either as a double-stranded, intertwined double helix (DSDH) or as a head-to-head single-stranded helix (HHSH). Current structure models are based on macromolecular X-ray crystallography (MX) and nuclear magnetic resonance (NMR). However, the HHSH form has only been observed by NMR. The shape and size of the different gramicidin conformations differ. We speculated therefore that reconstituting it into a lipidic mesophase with bilayers of different microstructures would preferentially stabilize one form over the other. By using such mesophases for in meso crystallogenesis, the expectation was that at least one would generate crystals of gramicidin in the HHSH form for structure determination by MX. This was tested using commercial and in-house synthesized lipids that support in meso crystallogenesis. Lipid acyl chain lengths were varied from 14 to 18 carbons to provide mesophases with a range of bilayer thicknesses. Unexpectedly, all lipids produced high-quality, structure-grade crystals with gramicidin only in the DSDH conformation.