Structural basis underlying the electron transfer features of a blue copper protein auracyanin from the photosynthetic bacterium Roseiflexus castenholzii

Wang, Chao; Xin, Yueyong; Min, Zhenzhen; Qi, Junjie; Zhang, Chenyun; Xu, Xiaoling

doi:10.1007/s11120-020-00709-y

Cited by 6 publications

(12 citation statements)

References 43 publications

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“…Previous enzymatic analyses confirmed the activity of photosynthetic ACIII as a menaquinol:auracyanin or cyt c oxidoreductase (9). Recently, we revealed that R. castenholzii ACIII oxidizes menaquinol-4 or menaquinol-7 and transfers electrons to its periplasmic electron acceptor auracyanin (24). It has been revealed that there is a single quinol binding site in R. marinus ACIII by isothermal titration calorimetry experiments (17).…”

Section: Discussionmentioning

confidence: 55%

“…S6, A to C), as well as the spatial distribution of the six hemes ( Fig. 2, A to C), electrons can be sequentially transferred along a wire that begins with the heme_1 in ActA and ends with the monoheme in the ActE subunit, and then eventually to the acceptor auracyanin (13,24).…”

Section: Composition and Overall Structurementioning

confidence: 99%

“…Our previous structure of the R. castenholzii core complex ( rc RC-LH) revealed a previously unknown architecture and a new type of menaquinone shuttling channel in the bacterial RC-LHs and illustrated the molecular basis underlying the LH and energy transfer mechanisms of early prokaryotes ( 23 ). We then extracted and purified R. castenholzii ACIII and its periplasmic electron acceptor auracyanin and revealed that ACIII oxidizes menaquinol-4 or menaquinol-7 and transfers the electrons to the copper ion coordinated in auracyanin ( 24 ). Here, we report the structures of the six-subunit R. castenholzii ACIII in air-oxidized and dithionite-reduced states, determined by single-particle cryo–electron microscopy (cryo-EM) at 3.3- and 3.5-Å resolution, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Cryo-EM structures of the air-oxidized and dithionite-reduced photosynthetic alternative complex III from Roseiflexus castenholzii

et al. 2020

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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 Roseiflexus castenholzii 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.

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Section: Discussionmentioning

confidence: 55%

Section: Composition and Overall Structurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cryo-EM structures of the air-oxidized and dithionite-reduced photosynthetic alternative complex III from Roseiflexus castenholzii

et al. 2020

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“…Isolation and purification of endogenous auracyanin (Ac) from Roseiflexus castenholzii was carried out by the methods as described (Wang et al, 2020). Before the oxidation assay, the purified Ac was treated with sodium dithionite to obtain the reduced Ac.…”

Section: Auracyanin Oxidation Assaysmentioning

confidence: 99%

Carotenoid assembly regulates quinone diffusion and theRoseiflexus castenholziireaction center-light harvesting complex architecture

Xin

Shi

Zhang

et al. 2023

Preprint

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Carotenoid (Car) pigments perform central roles in photosynthesis-related light harvesting (LH), photoprotection, and assembly of functional pigment-protein complexes. However, the relationships between Car depletion in the LH, assembly of the prokaryotic reaction center (RC)-LH complex, and quinone exchange are not fully understood. Here, we analyzed native RC-LH (nRC-LH) and Car-depleted RC-LH (dRC-LH) complexes inRoseiflexus castenholzii, a chlorosome-less filamentous anoxygenic phototroph that forms the deepest branch of photosynthetic bacteria. Newly identified exterior Cars functioned with the bacteriochlorophyll B800 to block the proposed quinone channel between LHαβ subunits in the nRC-LH, forming a sealed LH ring that was disrupted by transmembrane helices from cytochrome c and subunit X to allow quinone shuttling. dRC-LH lacked subunit X, leading to an exposed LH ring with a larger opening, which together accelerated the quinone exchange rate. We also assigned amino acid sequences of subunit X and two hypothetical proteins Y and Z that functioned in forming the quinone channel and stabilizing the RC-LH interactions. This study reveals the structural basis by which Cars assembly regulates the architecture and quinone exchange of bacterial RC-LH complexes. These findings mark an important step forward in understanding the evolution and diversity of prokaryotic photosynthetic apparatus.

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“…The last inserts into the opened LH ring to form a quinol-shuttling channel, through which MQH 2 reduced by the RC diffuses into the membrane quinone pool. Interestingly, the multi-subunit rc ACIII complex functionally replaces the bc 1 / b 6 f complex, oxidizing MQH 2 and transferring electrons to a periplasmic blue-copper protein, auracyanin ( rc Ac) ( Tsukatani et al., 2009 ; Wang et al., 2020 ). rc Ac is proposed to reduce the rc RC, forming a complete cyclic ETC.…”

Section: Introductionmentioning

confidence: 99%

A cytochrome c551 mediates the cyclic electron transport chain of the anoxygenic phototrophic bacterium Roseiflexus castenholzii

Yu,

Min,

Liu

et al. 2024

Plant Communications

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Structural basis underlying the electron transfer features of a blue copper protein auracyanin from the photosynthetic bacterium Roseiflexus castenholzii

Cited by 6 publications

References 43 publications

Cryo-EM structures of the air-oxidized and dithionite-reduced photosynthetic alternative complex III from Roseiflexus castenholzii

Cryo-EM structures of the air-oxidized and dithionite-reduced photosynthetic alternative complex III from Roseiflexus castenholzii

Carotenoid assembly regulates quinone diffusion and theRoseiflexus castenholziireaction center-light harvesting complex architecture

A cytochrome c551 mediates the cyclic electron transport chain of the anoxygenic phototrophic bacterium Roseiflexus castenholzii

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