4TQ2

Structure of S-type Phycobiliprotein Lyase CPES from Guillardia theta

Summary for 4TQ2

• Entry DOI: 10.2210/pdb4tq2/pdb
• Descriptor: Putative phycoerythrin lyase, HEXANE-1,6-DIOL (3 entities in total)
• Functional Keywords: beta barrel, lyase, phycoerythrobilin
• Biological source: Guillardia theta CCMP2712
• Total number of polymer chains: 1
• Total formula weight: 21778.36

Authors

Gasper, R.,Overkamp, K.E.,Frankenberg-Dinkel, N.,Hofmann, E. (deposition date: 2014-06-10, release date: 2014-08-13, Last modification date: 2024-10-23)

Primary citation

Overkamp, K.E.,Gasper, R.,Kock, K.,Herrmann, C.,Hofmann, E.,Frankenberg-Dinkel, N.
Insights into the Biosynthesis and Assembly of Cryptophycean Phycobiliproteins.
J.Biol.Chem., 289:26691-, 2014

PubMed Abstract: Phycobiliproteins are employed by cyanobacteria, red algae, glaucophytes, and cryptophytes for light-harvesting and consist of apoproteins covalently associated with open-chain tetrapyrrole chromophores. Although the majority of organisms assemble the individual phycobiliproteins into larger aggregates called phycobilisomes, members of the cryptophytes use a single type of phycobiliprotein that is localized in the thylakoid lumen. The cryptophyte Guillardia theta (Gt) uses phycoerythrin PE545 utilizing the uncommon chromophore 15,16-dihydrobiliverdin (DHBV) in addition to phycoerythrobilin (PEB). Both the biosynthesis and the attachment of chromophores to the apophycobiliprotein have not yet been investigated for cryptophytes. In this study, we identified and characterized enzymes involved in PEB biosynthesis. In addition, we present the first in-depth biochemical characterization of a eukaryotic phycobiliprotein lyase (GtCPES). Plastid-encoded HO (GtHo) was shown to convert heme into biliverdin IXα providing the substrate with a putative nucleus-encoded DHBV:ferredoxin oxidoreductase (GtPEBA). A PEB:ferredoxin oxidoreductase (GtPEBB) was found to convert DHBV to PEB, which is the substrate for the phycobiliprotein lyase GtCPES. The x-ray structure of GtCPES was solved at 2.0 Å revealing a 10-stranded β-barrel with a modified lipocalin fold. GtCPES is an S-type lyase specific for binding of phycobilins with reduced C15=C16 double bonds (DHBV and PEB). Site-directed mutagenesis identified residues Glu-136 and Arg-146 involved in phycobilin binding. Based on the crystal structure, a model for the interaction of GtCPES with the apophycobiliprotein CpeB is proposed and discussed.

PubMed: 25096577
DOI: 10.1074/jbc.M114.591131

Experimental method

X-RAY DIFFRACTION (1.95 Å)