Mills Deryck J, Vitt Stella, Strauss Mike, Shima Seigo, Vonck Janet
Department of Structural Biology , Max Planck Institute of Biophysics , Frankfurt , Germany.
Elife. 2013 Mar 5;2:e00218. doi: 10.7554/eLife.00218.
Methanogenic archaea use a [NiFe]-hydrogenase, Frh, for oxidation/reduction of F420, an important hydride carrier in the methanogenesis pathway from H2 and CO2. Frh accounts for about 1% of the cytoplasmic protein and forms a huge complex consisting of FrhABG heterotrimers with each a [NiFe] center, four Fe-S clusters and an FAD. Here, we report the structure determined by near-atomic resolution cryo-EM of Frh with and without bound substrate F420. The polypeptide chains of FrhB, for which there was no homolog, was traced de novo from the EM map. The 1.2-MDa complex contains 12 copies of the heterotrimer, which unexpectedly form a spherical protein shell with a hollow core. The cryo-EM map reveals strong electron density of the chains of metal clusters running parallel to the protein shell, and the F420-binding site is located at the end of the chain near the outside of the spherical structure. DOI:http://dx.doi.org/10.7554/eLife.00218.001.
产甲烷古菌利用一种[NiFe]氢化酶（Frh）来氧化/还原F420，F420是由H2和CO2生成甲烷途径中的一种重要氢化物载体。Frh约占细胞质蛋白的1%，并形成一个巨大的复合物，该复合物由具有各自[NiFe]中心、四个铁硫簇和一个FAD的FrhABG异源三聚体组成。在此，我们报告了通过近原子分辨率冷冻电镜确定的结合和未结合底物F420的Frh结构。对于没有同源物的FrhB的多肽链，从电子显微镜图谱中从头进行了追踪。这个1.2兆道尔顿的复合物包含12个异源三聚体拷贝，它们意外地形成了一个具有空心核心的球形蛋白壳。冷冻电镜图谱显示，与蛋白壳平行的金属簇链具有很强的电子密度，并且F420结合位点位于球形结构外部附近的链的末端。DOI:http://dx.doi.org/10.7554/eLife.00218.001 。
