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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Structure of the Nitrosomonas europaea Rh protein
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Structure of the Nitrosomonas europaea Rh protein

机译：亚硝基鸟Rh蛋白的结构

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Amt/MEP/Rh proteins are a family of integral membrane proteins implicated in the transport of NH_3, CH_2NH_2, and CO_2. Whereas Amt/MEP proteins are agreed to transport ammonia (NH_3/NH_4+), the primary substrate for Rh proteins has been controversial. Initial studies suggested that Rh proteins also transport ammonia, but more recent evidence suggests that they transport CO_2. Here we report the first structure of an Rh family member, the Rh protein from the chemolithoautotrophic ammonia-oxidizing bacterium Nitrosomonas europaea. This Rh protein exhibits a number of similarities to its Amt cousins, including a trimeric oligomeric state, a central pore with an unusual twin-His site in the middle, and a Phe residue that blocks the channel for small-molecule transport. However, there are some significant differences, the most notable being the presence of an additional cytoplasmic C-terminal α-helix, an increased number of internal proline residues along the trans-membrane helices, and a specific set of residues that appear to link the C-terminal helix to Phe blockage. This latter linkage suggests a mechanism in which binding of a partner protein to the C terminus could regulate channel opening. Another difference is the absence of the extracellular π-cation binding site conserved in Amt/Mep structures. Instead, CO_2 pressurization experiments identify a CO_2 binding site near the intracellular exit of the channel whose residues are highly conserved in all Rh proteins, except those belonging to the Rh30 subfamily. The implications of these findings on the functional role of the human Rh antigens are discussed.
机译：Amt / MEP / Rh蛋白是涉及NH_3，CH_2NH_2和CO_2转运的完整膜蛋白家族。尽管Amt / MEP蛋白被同意转运氨（NH_3 / NH_4 +），但Rh蛋白的主要底物仍存在争议。最初的研究表明Rh蛋白还可以转运氨，但是最近的证据表明它们可以转运CO_2。在这里，我们报告Rh家庭成员的第一个结构，来自化石自养氨氧化细菌欧洲硝化单胞菌的Rh蛋白。这种Rh蛋白与其Amt表亲具有许多相似之处，包括三聚体低聚状态，中央孔，中间有一个不寻常的Twin-His位点，以及一个Phe残基，该残基阻止了小分子运输的通道。但是，存在一些显着差异，最显着的是存在额外的胞质C末端α-螺旋，沿跨膜螺旋的内部脯氨酸残基数量增加以及一组似乎与之相关的残基。 C端螺旋对苯丙氨酸有阻滞作用。后者的联系暗示了一种机制，其中伴侣蛋白与C末端的结合可以调节通道的开放。另一个差异是在Amt / Mep结构中不存在保守的细胞外π阳离子结合位点。相反，CO_2加压实验在通道的细胞内出口附近发现了一个CO_2结合位点，其残基在所有Rh蛋白中都高度保守，除了属于Rh30亚家族的那些蛋白。讨论了这些发现对人类Rh抗原的功能作用的意义。

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