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-Structure paper
タイトル | Cryo-EM structure of HQNO-bound Alternative Complex III from the anoxygenic phototrophic bacterium Chloroflexus aurantiacus. |
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ジャーナル・号・ページ | Plant Cell, Year 2024 |
掲載日 | 2024年1月31日 |
著者 | Jiyu Xin / Zhenzhen Min / Lu Yu / Xinyi Yuan / Aokun Liu / Wenping Wu / Xin Zhang / Huimin He / Jingyi Wu / Yueyong Xin / Robert E Blankenship / Changlin Tian / Xiaoling Xu / |
PubMed 要旨 | Alternative complex III (ACIII) couples quinol oxidation and electron acceptor reduction with potential transmembrane proton translocation. It is compositionally and structurally different from the ...Alternative complex III (ACIII) couples quinol oxidation and electron acceptor reduction with potential transmembrane proton translocation. It is compositionally and structurally different from the cytochrome bc1/b6f complexes, but functionally replaces these enzymes in the photosynthetic and/or respiratory electron transport chains (ETCs) of many bacteria. However, the true compositions and architectures of ACIIIs remain unclear, as do their structural and functional relevance in mediating the ETCs. We here determined cryogenic electron microscopy structures of photosynthetic ACIII isolated from Chloroflexus aurantiacus (CaACIIIp), in apo-form and in complexed form bound to a menadiol analog 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO). Besides six canonical subunits (ActABCDEF), the structures revealed conformations of two previously unresolved subunits, ActG and I, which contributed to the complex stability. We also elucidated the structural basis of menaquinol oxidation and subsequent electron transfer along the [3Fe-4S]-6 hemes wire to its periplasmic electron acceptors, using electron paramagnetic resonance (EPR), spectroelectrochemistry, enzymatic analyses and molecular dynamics (MD) simulations. A unique insertion loop in ActE was shown to function in determining the binding specificity of CaACIIIp for downstream electron acceptors. This study broadens our understanding of the structural diversity and molecular evolution of ACIIIs, enabling further investigation of the (mena)quinol oxidoreductases evolved coupling mechanism in bacterial energy conservation. |
リンク | Plant Cell / PubMed:38299372 |
手法 | EM (単粒子) |
解像度 | 2.7 - 3.33 Å |
構造データ | EMDB-36984, PDB-8k9e: EMDB-36985, PDB-8k9f: EMDB-38012, PDB-8x2j: |
化合物 | ChemComp-HEC: ChemComp-SF4: ChemComp-F3S: ChemComp-EL6:
ChemComp-JLQ:
ChemComp-JL3:
ChemComp-JM9: ChemComp-MG: ChemComp-HQO: |
由来 |
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キーワード | MEMBRANE PROTEIN / Photosynthetic alternative complex III |