[Chromophore composition and nature of the absorption spectra of phycobiliproteins].

It was shown that phycobiliproteins are native pigment complexes, in which the protein quaternary structure is responsible for the aggregation of the chromophore groups covalently bound to the apoprotein. The main factor determining the structure of the phycobiliprotein absorption spectra is the excitone interaction of the chromophores, in which the number of bands in the spectrum is proportional to the number of interacting chromophores. In accordance with the number of bands (4) in the phycocyanobilin spectrum, i. e. chromophore of allophycocyanin and C-phycocyanin, and with the number of chromophores covalently linked to each one of the apoprotein molecules (2 for allophycocyanin and 3 for C-phycocyanin) their absorption spectra split into eight (2 X 4) and twelve (3 X 4) and twelve (3 X 4) bands, respectively. It is concluded that allophycocyanin is a native aggregate--dimer, while C-phycocyanin is a trimer of phycocyanobilin.