Light-harvesting photosynthetic bile pigment-protein from the phycobiliprotein complex. Allophycocyanin has a maximum absorption at approximately 654 nanometers. Heterohexamer of two alpha chains, one alpha-B chain and three beta chains. Forms the core of the phycobilisome. Contains one covalently linked phycocyanobilin chromophore (Probable). The chromophore is added by phycocyanobilin lyase CpcS 1. Belongs to the phycobiliprotein family.