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Respiratory complex I in mitochondrial membrane catalyzes oversized ubiquinones
NADH-ubiquinone (UQ) oxidoreductase (complex I) couples electron transfer from NADH to UQ with proton translocation in its membrane part. The UQ reduction step is key to triggering proton translocation. Structural studies have identified a long, narrow, tunnel-like cavity within complex I, through w...
Autores principales: | , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Society for Biochemistry and Molecular Biology
2023
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10416054/ https://www.ncbi.nlm.nih.gov/pubmed/37394006 http://dx.doi.org/10.1016/j.jbc.2023.105001 |
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author | Ikunishi, Ryo Otani, Ryohei Masuya, Takahiro Shinzawa-Itoh, Kyoko Shiba, Tomoo Murai, Masatoshi Miyoshi, Hideto |
author_facet | Ikunishi, Ryo Otani, Ryohei Masuya, Takahiro Shinzawa-Itoh, Kyoko Shiba, Tomoo Murai, Masatoshi Miyoshi, Hideto |
author_sort | Ikunishi, Ryo |
collection | PubMed |
description | NADH-ubiquinone (UQ) oxidoreductase (complex I) couples electron transfer from NADH to UQ with proton translocation in its membrane part. The UQ reduction step is key to triggering proton translocation. Structural studies have identified a long, narrow, tunnel-like cavity within complex I, through which UQ may access a deep reaction site. To elucidate the physiological relevance of this UQ-accessing tunnel, we previously investigated whether a series of oversized UQs (OS-UQs), whose tail moiety is too large to enter and transit the narrow tunnel, can be catalytically reduced by complex I using the native enzyme in bovine heart submitochondrial particles (SMPs) and the isolated enzyme reconstituted into liposomes. Nevertheless, the physiological relevance remained unclear because some amphiphilic OS-UQs were reduced in SMPs but not in proteoliposomes, and investigation of extremely hydrophobic OS-UQs was not possible in SMPs. To uniformly assess the electron transfer activities of all OS-UQs with the native complex I, here we present a new assay system using SMPs, which were fused with liposomes incorporating OS-UQ and supplemented with a parasitic quinol oxidase to recycle reduced OS-UQ. In this system, all OS-UQs tested were reduced by the native enzyme, and the reduction was coupled with proton translocation. This finding does not support the canonical tunnel model. We propose that the UQ reaction cavity is flexibly open in the native enzyme to allow OS-UQs to access the reaction site, but their access is obstructed in the isolated enzyme as the cavity is altered by detergent-solubilizing from the mitochondrial membrane. |
format | Online Article Text |
id | pubmed-10416054 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2023 |
publisher | American Society for Biochemistry and Molecular Biology |
record_format | MEDLINE/PubMed |
spelling | pubmed-104160542023-08-12 Respiratory complex I in mitochondrial membrane catalyzes oversized ubiquinones Ikunishi, Ryo Otani, Ryohei Masuya, Takahiro Shinzawa-Itoh, Kyoko Shiba, Tomoo Murai, Masatoshi Miyoshi, Hideto J Biol Chem Research Article NADH-ubiquinone (UQ) oxidoreductase (complex I) couples electron transfer from NADH to UQ with proton translocation in its membrane part. The UQ reduction step is key to triggering proton translocation. Structural studies have identified a long, narrow, tunnel-like cavity within complex I, through which UQ may access a deep reaction site. To elucidate the physiological relevance of this UQ-accessing tunnel, we previously investigated whether a series of oversized UQs (OS-UQs), whose tail moiety is too large to enter and transit the narrow tunnel, can be catalytically reduced by complex I using the native enzyme in bovine heart submitochondrial particles (SMPs) and the isolated enzyme reconstituted into liposomes. Nevertheless, the physiological relevance remained unclear because some amphiphilic OS-UQs were reduced in SMPs but not in proteoliposomes, and investigation of extremely hydrophobic OS-UQs was not possible in SMPs. To uniformly assess the electron transfer activities of all OS-UQs with the native complex I, here we present a new assay system using SMPs, which were fused with liposomes incorporating OS-UQ and supplemented with a parasitic quinol oxidase to recycle reduced OS-UQ. In this system, all OS-UQs tested were reduced by the native enzyme, and the reduction was coupled with proton translocation. This finding does not support the canonical tunnel model. We propose that the UQ reaction cavity is flexibly open in the native enzyme to allow OS-UQs to access the reaction site, but their access is obstructed in the isolated enzyme as the cavity is altered by detergent-solubilizing from the mitochondrial membrane. American Society for Biochemistry and Molecular Biology 2023-06-30 /pmc/articles/PMC10416054/ /pubmed/37394006 http://dx.doi.org/10.1016/j.jbc.2023.105001 Text en © 2023 The Authors https://creativecommons.org/licenses/by/4.0/This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Research Article Ikunishi, Ryo Otani, Ryohei Masuya, Takahiro Shinzawa-Itoh, Kyoko Shiba, Tomoo Murai, Masatoshi Miyoshi, Hideto Respiratory complex I in mitochondrial membrane catalyzes oversized ubiquinones |
title | Respiratory complex I in mitochondrial membrane catalyzes oversized ubiquinones |
title_full | Respiratory complex I in mitochondrial membrane catalyzes oversized ubiquinones |
title_fullStr | Respiratory complex I in mitochondrial membrane catalyzes oversized ubiquinones |
title_full_unstemmed | Respiratory complex I in mitochondrial membrane catalyzes oversized ubiquinones |
title_short | Respiratory complex I in mitochondrial membrane catalyzes oversized ubiquinones |
title_sort | respiratory complex i in mitochondrial membrane catalyzes oversized ubiquinones |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10416054/ https://www.ncbi.nlm.nih.gov/pubmed/37394006 http://dx.doi.org/10.1016/j.jbc.2023.105001 |
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