Regulating Light-Harvesting Protein Assembly through Engineered Trimers of Phycocyanin and Allophycocyanin
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Phycobiliproteins form oligomeric assemblies essential for photosynthetic light harvesting. Here, we engineered phycocyanin (TeCPC) and allophycocyanin (TeAPC) from Thermosynechococcus elongatus to stabilize defined trimers by inhibiting hexamer formation. Structure-guided substitutions at conserved glycine residues (TeCPC G29R, TeAPC G21R) introduce steric hindrance at the hexamer interface. Recombinant expression in Escherichia coli produced holoproteins with native-like chromophorylation. Biophysical and structural analyses confirmed homogeneous trimer formation and absence of higher-order assemblies. Thermal measurements indicated cooperative unfolding, supporting structural uniformity. These engineered trimers provide robust models for studying energy transfer in phycobiliproteins.
