6LOE

Cryo-EM structure of the dithionite-reduced photosynthetic alternative complex III from Roseiflexus castenholzii

Summary for 6LOE

• Entry DOI: 10.2210/pdb6loe/pdb
• Related: 6LOD
• EMDB information: 0936 0937
• Descriptor: MULTIHEME_CYTC domain-containing protein, [(2S)-2-octadecanoyloxypropyl] octadecanoate, Fe-S-cluster-containing hydrogenase components 1-like protein, ... (10 entities in total)
• Functional Keywords: quinol:electron acceptor oxidoreductase, photosynthesis
• Biological source: Roseiflexus castenholzii (strain DSM 13941 / HLO8); More
• Total number of polymer chains: 6
• Total formula weight: 274679.54

Authors

Shi, Y.,Xin, Y.Y.,Wang, C.,Blankenship, R.E.,Sun, F.,Xu, X.L. (deposition date: 2020-01-05, release date: 2020-11-04, Last modification date: 2025-09-17)

Primary citation

Shi, Y.,Xin, Y.,Wang, C.,Blankenship, R.E.,Sun, F.,Xu, X.
Cryo-EM structures of the air-oxidized and dithionite-reduced photosynthetic alternative complex III from Roseiflexus castenholzii .
Sci Adv, 6:eaba2739-eaba2739, 2020

PubMed Abstract: Alternative complex III (ACIII) is a multisubunit quinol:electron acceptor oxidoreductase that couples quinol oxidation with transmembrane proton translocation in both the respiratory and photosynthetic electron transport chains of bacteria. The coupling mechanism, however, is poorly understood. Here, we report the cryo-EM structures of air-oxidized and dithionite-reduced ACIII from the photosynthetic bacterium at 3.3- and 3.5-Å resolution, respectively. We identified a menaquinol binding pocket and an electron transfer wire comprising six hemes and four iron-sulfur clusters that is capable of transferring electrons to periplasmic acceptors. We detected a proton translocation passage in which three strictly conserved, mid-passage residues are likely essential for coupling the redox-driven proton translocation across the membrane. These results allow us to propose a previously unrecognized coupling mechanism that links the respiratory and photosynthetic functions of ACIII. This study provides a structural basis for further investigation of the energy transformation mechanisms in bacterial photosynthesis and respiration.

PubMed: 32832681
DOI: 10.1126/sciadv.aba2739

Experimental method

ELECTRON MICROSCOPY (3.5 Å)