Biosynthesis and characterization of a recombinant eukaryotic allophycocyanin using prokaryotic accessory enzymes

Phycobiliproteins (PBPs) are colored fluorescent proteins present in cyanobacteria, red alga, and cryptophyta. These proteins have many potential uses in biotechnology going from food colorants to medical applications. Allophycocyanin, the simplest PBP, is a heterodimer of αβ subunits that oligomerizes as a trimer (αβ)₃ . Each subunit contains a phycocyanobilin, bound to a cysteine residue, which is responsible for its spectroscopic properties. In this article, we are reporting the expression of recombinant allophycocyanin (rAPC) from the eukaryotic red algae Agarophyton chilensis in Escherichia coli, using prokaryotic accessory enzymes to obtain a fully functional rAPC. Three duet vectors were used to include coding sequences of α and β subunits from A. chilensis and accessorial enzymes (heterodimeric lyase cpc S/U, heme oxygenase 1, phycocyanobilin oxidoreductase) from cyanobacteria Arthrospira maxima. rAPC was purified using several chromatographic steps. The characterization of the pure rAPC indicates very similar spectroscopic properties, λ_max^Abs , λ_max^Em , fluorescence lifetime, and chromophorylation degree, with native allophycocyanin (nAPC) from A. chilensis. This method, to produce high-quality recombinant allophycocyanin, can be used to express and characterize other macroalga phycobiliproteins, to be used for biotechnological or biomedical purposes.