Allophycocyanin and phycocyanin crystal structures reveal facets of phycobilisome assembly

► Assembly of the phycobilisome is still poorely understood. ► Minor structural variances appear to facilitate hexamer formation. ► Five new phycocyanin and allophycocyanin crystal structures are presented. ► The structures reveal new attributes that lead to or inhibit hexamer formation. ► The small core linker protein modifies the allophycocyanin hexamer assembly.