Light-harvesting photosynthetic bile pigment-protein from the phycobiliprotein complex (phycobilisome, PBS). Phycocyanin is the major phycobiliprotein in the PBS rod. Heterodimer of an alpha and a beta subunit (PubMed:8168545). Dimers further assemble into trimers and the trimers into hexamers. The basic functional unit of phycobiliproteins is a ring-shaped hexamer formed from two back-to-back trimers contacting via the alpha chain subunits. The trimers are composed of alpha/beta subunit heterodimers arranged around a three-fold axis of symmetry. The phycoerythrins also contain a gamma subunit which is located in the center of the hexamer (By similarity). Part of the phycobilisome rod. Contains one covalently linked phycocyanobilin chromophore. Belongs to the phycobiliprotein family.