Biosynthesis of C-phycocyanin trimers

Area of Science:

• Biochemistry and Molecular Biology
• Synthetic Biology
• Photosynthesis Research

Background:

• Phycobiliproteins, like C-phycocyanin (CPC), are crucial light-harvesting complexes in cyanobacteria.
• Efficient light capture and energy transfer by CPC are vital for photosynthesis.
• Large-scale production of functional CPC is challenging due to complex chromophore attachment.

Purpose of the Study:

• To develop a method for the biosynthesis of functional C-phycocyanin (CPC) in E. coli.
• To overcome challenges in the sequential covalent attachment of phycocyanobilin (PCB) chromophores.
• To engineer CPC with tailored light-harvesting and energy transfer properties.

Main Methods:

• Utilized a dual-promoter (T7 and araBAD) system for controlled, sequential PCB chromophore binding.
• Achieved biosynthesis of β-C-phycocyanin (β-CPC) with specific chromophore attachments in E. coli.
• Investigated the assembly of α-CPC with modified β-subunits to form CPC trimers.

Main Results:

• Successfully synthesized functional β-CPC in E. coli, demonstrating energy transfer from β153-PCB to β82-PCB.
• Identified that only β-subunits with covalently bound PCB pairs (PCB₂-β) assemble into complete CPC trimers.
• The assembled CPC trimers exhibit native-like structure, precise chromophore arrangement, and efficient light-harvesting (λ_{max, absorption} = 617 nm, λ_{max, emission} = 646 nm).

Conclusions:

• Established a robust biosynthetic pathway for CPC trimers in E. coli.
• The developed system facilitates the engineering of phycobiliproteins for enhanced light-harvesting capabilities.
• This work supports advancements in artificial photosynthesis, antenna design, and energy transfer studies.