6BTM image
Entry Detail
PDB ID:
6BTM
EMDB ID:
Title:
Structure of Alternative Complex III from Flavobacterium johnsoniae (Wild Type)
Biological Source:
PDB Version:
Deposition Date:
2017-12-07
Release Date:
2018-05-09
Method Details:
Experimental Method:
Resolution:
3.40 Å
Aggregation State:
PARTICLE
Reconstruction Method:
SINGLE PARTICLE
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Alternative Complex III subunit A
Chain IDs:A
Chain Length:444
Number of Molecules:1
Biological Source:Flavobacterium johnsoniae UW101
Polymer Type:polypeptide(L)
Description:Alternative Complex III subunit B
Chain IDs:B
Chain Length:949
Number of Molecules:1
Biological Source:Flavobacterium johnsoniae UW101
Polymer Type:polypeptide(L)
Description:Alternative Complex III subunit C
Chain IDs:C
Chain Length:466
Number of Molecules:1
Biological Source:Flavobacterium johnsoniae UW101
Polymer Type:polypeptide(L)
Description:Alternative Complex III subunit D
Chain IDs:D
Chain Length:174
Number of Molecules:1
Biological Source:Flavobacterium johnsoniae UW101
Polymer Type:polypeptide(L)
Description:Alternative Complex III subunit E
Chain IDs:E
Chain Length:162
Number of Molecules:1
Biological Source:Flavobacterium johnsoniae UW101
Polymer Type:polypeptide(L)
Description:Alternative Complex III subunit F
Chain IDs:F
Chain Length:464
Number of Molecules:1
Biological Source:Flavobacterium johnsoniae UW101
Primary Citation
Structure of the alternative complex III in a supercomplex with cytochrome oxidase.
Nature 557 123 126 (2018)
PMID: 29695868 DOI: 10.1038/s41586-018-0061-y

Abstact

Alternative complex III (ACIII) is a key component of the respiratory and/or photosynthetic electron transport chains of many bacteria1-3. Like complex III (also known as the bc1 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 similarity4-7. 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 8 , including the proton pump polysulfide reductase9,10. We isolated the ACIII from Flavobacterium johnsoniae with native lipids using styrene maleic acid copolymer11-14, both as an independent enzyme and as a functional 1:1 supercomplex with an aa3-type cytochrome c oxidase (cyt aa3). 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 aa3 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.

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