A cytochrome c551 mediates the cyclic electron transport chain of the anoxygenic phototrophic bacterium Roseiflexus castenholzii.
Plant Commun
; 5(2): 100715, 2024 Feb 12.
Article
en En
| MEDLINE
| ID: mdl-37710959
ABSTRACT
Roseiflexus castenholzii is a gram-negative filamentous phototrophic bacterium that carries out anoxygenic photosynthesis through a cyclic electron transport chain (ETC). The ETC is composed of a reaction center (RC)-light-harvesting (LH) complex (rcRC-LH); an alternative complex III (rcACIII), which functionally replaces the cytochrome bc1/b6f complex; and the periplasmic electron acceptor auracyanin (rcAc). Although compositionally and structurally different from the bc1/b6f complex, rcACIII plays similar essential roles in oxidizing menaquinol and transferring electrons to the rcAc. However, rcACIII-mediated electron transfer (which includes both an intraprotein route and a downstream route) has not been clearly elucidated, nor have the details of cyclic ETC. Here, we identify a previously unknown monoheme cytochrome c (cyt c551) as a novel periplasmic electron acceptor of rcACIII. It reduces the light-excited rcRC-LH to complete a cyclic ETC. We also reveal the molecular mechanisms involved in the ETC using electron paramagnetic resonance (EPR), spectroelectrochemistry, and enzymatic and structural analyses. We find that electrons released from rcACIII-oxidized menaquinol are transferred to two alternative periplasmic electron acceptors (rcAc and cyt c551), which eventually reduce the rcRC to form the complete cyclic ETC. This work serves as a foundation for further studies of ACIII-mediated electron transfer in anoxygenic photosynthesis and broadens our understanding of the diversity and molecular evolution of prokaryotic ETCs.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Proteínas Bacterianas
/
Grupo Citocromo c
/
Chloroflexi
/
Citocromos c
Idioma:
En
Revista:
Plant Commun
Año:
2024
Tipo del documento:
Article
País de afiliación:
China