22VH

The assembled CPC trimer

Summary for 22VH

• Entry DOI: 10.2210/pdb22vh/pdb
• Descriptor: C-phycocyanin alpha subunit, C-phycocyanin beta subunit, PHYCOCYANOBILIN, ... (4 entities in total)
• Functional Keywords: phycocyanin, light-harvesting, energy-transfer, photosynthesis
• Biological source: Nostoc sp. PCC 7120 = FACHB-418; More
• Total number of polymer chains: 12
• Total formula weight: 250175.14

Authors

Zhao, x.,Zhu, j.x.,Xue, c.y.,Zheng, x.y.,Zhao, k.h. (deposition date: 2026-01-25, release date: 2026-08-19)

Primary citation

Zhao, X.,Zhu, J.X.,Li, G.C.,Zhao, K.H.
Biosynthesis of C-phycocyanin trimers.
Biochim Biophys Acta Bioenerg, 1867:149599-149599, 2026

PubMed Abstract: Phycobiliproteins, particularly C-phycocyanin (CPC), serve as major light-harvesting complexes in cyanobacteria, exhibiting high efficiency in light-harvesting and energy transfer. Currently, the easy and large-scale acquisition of functional CPC remains a major challenge, primarily due to the requirement for precise, sequential covalent attachment of multiple phycocyanobilin (PCB) chromophores. In this study, by using a dual-promoter (T7 and araBAD) system to control the sequential binding of two PCB chromophores to β82 and β153, we successfully achieved the biosynthesis of β-CPC (λ = 605 nm, λ = 644 nm) in E. coli, which can transfer energy from the β153-PCB to the β82-PCB. The assembly of α-CPC with PCB-β82, PCB-β153, and PCB-β under identical conditions indicates that only PCB-β, which covalently binds the two PCB chromophores, can assemble with α-CPC to form a complete CPC trimer (λ = 617 nm, λ = 646 nm). The structure of the assembled trimer reveals that it adopts a typical phycobiliprotein fold, with multiple chromophores precisely arranged, exhibiting features highly similar to those of native CPC. Furthermore, we established a biosynthetic pathway for CPC trimers in E. coli. This system provides a powerful tool for engineering phycobiliproteins with various light-harvesting and energy transfer properties, facilitating future studies on artificial photosynthesis, light-harvesting antenna design, and the fundamental mechanisms of excitation energy transfer.

PubMed: 42336025
DOI: 10.1016/j.bbabio.2026.149599

Experimental method

X-RAY DIFFRACTION (2.5 Å)