8GTH

Crystal strucuture of cyt c551 from anoxygenic phototrophic bacterium Roseiflexus castenholzii

Summary for 8GTH

• Entry DOI: 10.2210/pdb8gth/pdb
• Descriptor: Cytochrome c class I, HEME C (2 entities in total)
• Functional Keywords: electron transfer protein, electron transport
• Biological source: Roseiflexus castenholzii DSM 13941
• Total number of polymer chains: 6
• Total formula weight: 77322.93

Authors

Min, Z.Z.,Meng, H.L.,Xu, X.L. (deposition date: 2022-09-08, release date: 2023-09-13, Last modification date: 2024-11-06)

Primary citation

Yu, L.,Min, Z.,Liu, M.,Xin, Y.,Liu, A.,Kuang, J.,Wu, W.,Wu, J.,He, H.,Xin, J.,Blankenship, R.E.,Tian, C.,Xu, X.
A cytochrome c 551 mediates the cyclic electron transport chain of the anoxygenic phototrophic bacterium Roseiflexus castenholzii.
Plant Commun., 5:100715-100715, 2024

PubMed 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 bc/bf complex; and the periplasmic electron acceptor auracyanin (rcAc). Although compositionally and structurally different from the bc/bf 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 c) 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 c), 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.

PubMed: 37710959
DOI: 10.1016/j.xplc.2023.100715

Experimental method

X-RAY DIFFRACTION (3.1 Å)