Crystal structure of phycoerythrin from cyanobacterium Nostoc sp. WR13 contains multiple stacks of hexameric assemblies which resemble the rods of phycobilisome.

2-(2-{2-[2-(2-{2-[2-(2-ETHOXY-ETHOXY)-ETHOXY]-ETHOXY}-ETHOXY)-ETHOXY]-ETHOXY}-ETHOXY)-ETHANOL; POLYETHYLENE GLYCOL PEG400

PEG-MME fragment n=12;polyethylene glycol monomethyl ether fragment n=12;PEG 550 MME

The crystal stacks of hexameric assemblies of phycoerythrin from cyanobacterium Nostoc sp. WR13 resemble rods of phycobilisome

There are two phycoerythrobilin chromophore molecules (called PEB) in the alpha subunit of phycoerythrin. They are covalently bound to residues Cys82 (PEB166) and Cys139 (PEB167) of the alpha subunit, respectively.
Alpha subunit of cyanobacterial protein phycoerythrin

There are three phycoerythrobilin chromophore molecules (called PEB) in the beta subunit of phycoerythrin. They are covalently bound to residues Cys80 (PEB186), Cys165 (PEB187) and Cys48/Cys59 (PEB188) of the beta subunit.
Beta subunit of cyanobacterial protein phycoerythrin

From the desert Rann of Kachchh (RoK), Gujarat, India

Morpheus screen condition C9:
10% w/v PEG 20 000, 20% v/v PEG MME 550 precipitants;
0.03 M NPS (Nitrate, Phosphate & Sulfate) mix of additives;
0.01 M bicine/Trizma base pH 8.5 buffer system

Department of Energy (DOE, United States)
DE-SC0001035 (Office of Basic Energy Sciences)

Department of Biotechnology (DBT, India)
BT/PR15686/AAQ/3/811/2016 (UGC-BSR Faculty Fellowship)

BT/IN/UK/DBT-BC/2017-18 (Newton-Bhabha fellowship)

In vivo the hexamers are stacked to constitute portions of the phycobillisome rods.
Hydrogens have been added in their riding positions
Allophycocyanin crystal structure Phycobilisome Phycobiliproteins Phycocyanobilin chromophore Light harvesting complex Cyanobacterium Nostoc sp. WR13, PHOTOSYNTHESIS