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Structure of the alternative complex III in a supercomplex with cytochrome oxidase.
- Source :
-
Nature [Nature] 2018 May; Vol. 557 (7703), pp. 123-126. Date of Electronic Publication: 2018 Apr 25. - Publication Year :
- 2018
-
Abstract
- Alternative complex III (ACIII) is a key component of the respiratory and/or photosynthetic electron transport chains of many bacteria <superscript>1-3</superscript> . Like complex III (also known as the bc <subscript>1</subscript> complex), ACIII catalyses the oxidation of membrane-bound quinol and the reduction of cytochrome c or an equivalent electron carrier. However, the two complexes have no structural similarity <superscript>4-7</superscript> . Although ACIII has eluded structural characterization, several of its subunits are known to be homologous to members of the complex iron-sulfur molybdoenzyme (CISM) superfamily <superscript>8</superscript> , including the proton pump polysulfide reductase <superscript>9,10</superscript> . We isolated the ACIII from Flavobacterium johnsoniae with native lipids using styrene maleic acid copolymer <superscript>11-14</superscript> , both as an independent enzyme and as a functional 1:1 supercomplex with an aa <subscript>3</subscript> -type cytochrome c oxidase (cyt aa <subscript>3</subscript> ). We determined the structure of ACIII to 3.4 Å resolution by cryo-electron microscopy and constructed an atomic model for its six subunits. The structure, which contains a [3Fe-4S] cluster, a [4Fe-4S] cluster and six haem c units, shows that ACIII uses known elements from other electron transport complexes arranged in a previously unknown manner. Modelling of the cyt aa <subscript>3</subscript> component of the supercomplex revealed that it is structurally modified to facilitate association with ACIII, illustrating the importance of the supercomplex in this electron transport chain. The structure also resolves two of the subunits of ACIII that are anchored to the lipid bilayer with N-terminal triacylated cysteine residues, an important post-translational modification found in numerous prokaryotic membrane proteins that has not previously been observed structurally in a lipid bilayer.
- Subjects :
- Cysteine chemistry
Cysteine metabolism
Cytochrome c Group metabolism
Cytochromes a metabolism
Cytochromes a3 metabolism
Electron Transport Complex III metabolism
Heme analogs & derivatives
Heme chemistry
Lipid Bilayers chemistry
Lipid Bilayers metabolism
Lipids chemistry
Models, Molecular
Nanostructures chemistry
Nanostructures ultrastructure
Oxidation-Reduction
Protein Subunits chemistry
Protein Subunits metabolism
Cryoelectron Microscopy
Cytochrome c Group chemistry
Cytochrome c Group ultrastructure
Cytochromes a chemistry
Cytochromes a ultrastructure
Cytochromes a3 chemistry
Cytochromes a3 ultrastructure
Electron Transport Complex III chemistry
Electron Transport Complex III ultrastructure
Flavobacterium enzymology
Subjects
Details
- Language :
- English
- ISSN :
- 1476-4687
- Volume :
- 557
- Issue :
- 7703
- Database :
- MEDLINE
- Journal :
- Nature
- Publication Type :
- Academic Journal
- Accession number :
- 29695868
- Full Text :
- https://doi.org/10.1038/s41586-018-0061-y