Rod linker protein, connecting hexameric phycocyanin (PC, made by cpcA and cpcB) rods in the phycobilisome (PBS). PC is the major phycobiliprotein in PBS rods. 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. Part of 2 PBS rod complexes, the conventional CpcG-PBS rod and a photosystem I-specific CpcL-PBS rod, both of which include ferredoxin--NADP reductase (petH). CpcG-PBS has on average 3 stacked phycocyanin hexamers (PC, CpcA and CpcB). Linker CpcG connects the PC stack to the thylakoid, the hexamers are linked by 1 copy of CpcC1, 1 copy of CpcC2 and the stack is terminated by a single copy of CpcD. The CpcL-PBS has on average 5 stacked phycocyanin hexamers (PC, CpcA and CpcB). Linker CpcL connects the PC stack to the thylakoid, the hexamers are linked by 1 copy of CpcC1, 3 copies of CpcC2 and the stack is terminated by a single copy of CpcD. This protein occurs in the rod, it is associated with phycocyanin. Belongs to the phycobilisome linker protein family.