Evolutionary Conservation in Biogenesis of β-Barrel Proteins Allows Mitochondria to Assemble a Functional Bacterial Trimeric Autotransporter Protein*
Evolutionary Conservation in Biogenesis of β-Barrel Proteins Allows Mitochondria to Assemble a Functional Bacterial Trimeric Autotransporter Protein*
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DOI：
10.1074/jbc.m114.565655
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发表时间：
2014-09
期刊：
影响因子：
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通讯作者：
T. Ulrich;Philipp Oberhettinger;M. Schütz;Katharina Holzer;A. S. Ramms;D. Linke;I. Autenrieth;D. Rapaport
中科院分区：
文献类型：
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作者：
T. Ulrich;Philipp Oberhettinger;M. Schütz;Katharina Holzer;A. S. Ramms;D. Linke;I. Autenrieth;D. Rapaport
背景：β-桶蛋白存在于革兰氏阴性细菌、线粒体和叶绿体的外膜中。结果：线粒体能够以功能形式组装细菌三聚体自转运蛋白 YadA。结论：BAM 机制的脂蛋白并不是自转运蛋白生物合成所绝对必需的。意义：线粒体与细菌的进化联系使得前者甚至能够处理原核生物特异性蛋白质。耶尔森氏菌粘附素 A (YadA) 属于一类形成三聚体结构的细菌粘附素。它们的成熟形式包含一个过客结构域和一个将蛋白质锚定在外膜 (OM) 的 C 端 β 结构域。人们对这些蛋白质的前体如何穿过周质并组装成 OM 知之甚少。在本研究中，我们利用了细菌和线粒体之间β-桶蛋白生物发生中的进化保守性。我们之前观察到，在酵母细胞中表达后，包括 YadA 跨膜结构域的细菌 β-桶蛋白组装成线粒体 OM。在当前的研究中，我们发现，当在酵母细胞中表达时，全长 YadA 的单体和三聚体形式都可以在线粒体中检测到，但只有三聚体完全整合到 OM 中。寡聚形式以其天然构象暴露在细胞器表面，并保持其粘附宿主细胞的能力。 YadA 与细菌周质伴侣 Skp 的线粒体靶向形式共表达，但不与 SurA 或 SecB 共表达，导致两种形式的 YadA 水平增强。总而言之，这些结果表明，三聚体自转运蛋白的正确组装也可以发生在缺乏 BAM 机制脂蛋白的系统中，并且可以通过分子伴侣 Skp 特异性增强。
Background: β-Barrel proteins are found in the outer membrane of Gram-negative bacteria, mitochondria, and chloroplasts. Results: Mitochondria are able to assemble the bacterial trimeric autotransporter YadA in a functional form. Conclusion: The lipoproteins of the BAM machinery are not absolutely required for the biogenesis of autotransporter protein. Significance: The evolutionary link of mitochondria to bacteria allows the former to process even prokaryotic-specific proteins. Yersinia adhesin A (YadA) belongs to a class of bacterial adhesins that form trimeric structures. Their mature form contains a passenger domain and a C-terminal β-domain that anchors the protein in the outer membrane (OM). Little is known about how precursors of such proteins cross the periplasm and assemble into the OM. In the present study we took advantage of the evolutionary conservation in the biogenesis of β-barrel proteins between bacteria and mitochondria. We previously observed that upon expression in yeast cells, bacterial β-barrel proteins including the transmembrane domain of YadA assemble into the mitochondrial OM. In the current study we found that when expressed in yeast cells both the monomeric and trimeric forms of full-length YadA were detected in mitochondria but only the trimeric species was fully integrated into the OM. The oligomeric form was exposed on the surface of the organelle in its native conformation and maintained its capacity to adhere to host cells. The co-expression of YadA with a mitochondria-targeted form of the bacterial periplasmic chaperone Skp, but not with SurA or SecB, resulted in enhanced levels of both forms of YadA. Taken together, these results indicate that the proper assembly of trimeric autotransporter can occur also in a system lacking the lipoproteins of the BAM machinery and is specifically enhanced by the chaperone Skp.