Crystal structure of a phycourobilin-containing phycoerythrin at 1.90-Å resolution

Stephan Ritter, Roger G. Hiller, Pamela M. Wrench, Wolfram Welte, Kay Diederichs*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

67 Citations (Scopus)


The structure of R-phycoerythrin (R-PE) from the red alga Griffithsia monilis was solved at 1.90-Å resolution by molecular replacement, using the atomic coordinates of cyanobacterial phycocyanin from Fremyella diplosiphon as a model. The crystallographic R factor for the final model is 17.5% (R(free) 22.7%) for reflections in the range 100-1.90 Å. The model consists of an (αβ)2 dimer with an internal noncrystallographic dyad and a fragment of the γ-polypeptide. The α-polypeptide (164 amino acid residues) has two covalently bound phycoerythrobilins at positions α82 and α139. The β- polypeptide (177 residues) has two phycoerythrobilins bound to residues β82 and β158 and one phycourobilin covalently attached to rings A and D at residues β50 and β61, respectively. The electron density of the γ- polypeptide is mostly averaged out by threefold crystallographic symmetry, but a dipeptide (Gly-Tyr) and one single Tyr could be modeled. These two tyrosine residues of the γ-polypeptide are in close proximity to the phycoerythrobilins at position β82 of two symmetry-related β-polypeptides and are related by the same noncrystallographic dyad as the (αβ)2 dimer. Possible energy transfer pathways are discussed briefly.

Original languageEnglish
Pages (from-to)86-97
Number of pages12
JournalJournal of Structural Biology
Issue number2
Publication statusPublished - 15 Jun 1999


  • light-harvesting complexes
  • molecular replacement
  • phycobiliproteins
  • protein structure
  • red algae

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