Light-harvesting photosynthetic bile pigment-protein from the phycobiliprotein complex. Allophycocyanin has a maximum absorption at approximately 654 nanometers (By similarity). Heterohexamer of two alpha chains, one alpha-B chain and three beta chains. Forms the core of the phycobilisome. Contains one covalently linked bilin chromophore. Increased levels of phycobilisomes (PBS) and photosystem I (PSI), decreased levels of photosystem II (PSII) per cell. Cells are unable to undergo state transitions. When combined with an ApcF deletion mutant the cells have decreased PBS, PSI and PSII, and require glucose to grow. Belongs to the phycobiliprotein family.