A variant beta-allophycocyanin (AP) which forms a complex with ApcE, a phycobilisome terminal emitter that influences energy transfer to photosystem II. Heterodimer of ApcE and this beta chain. Contains one covalently linked bilin chromophore. Increased levels of photosystem I (PSI), decreased levels of phycobilisomes (PBS) and photosystem II (PSII) per cell. Cells are unable to undergo state transitions. When combined with an ApcD deletion mutant the cells have decreased PBS, PSI and PSII, and require glucose to grow. Belongs to the phycobiliprotein family.