Rod-core linker protein required for attachment of phycocyanin to allophycocyanin in cores of phycobilisomes. Linker polypeptides determine the state of aggregation and the location of the disk-shaped phycobiliprotein units within the phycobilisome and modulate their spectroscopic properties in order to mediate a directed and optimal energy transfer. The phycobilisome is a hemidiscoidal structure that is composed of two distinct substructures: a core complex and a number of rods radiating from the core. Although originally identified as Cyanidium caldarium, these sequences derive from Galdieria sulphuraria. Belongs to the phycobilisome linker protein family.