PDBsum entry 3o2c

Photosynthesis

PDB id: 3o2c

Contents

Protein chains

162 a.a. *

172 a.a. *

Ligands

CYC ×3

Waters ×459

* Residue conservation analysis

PDB id:

3o2c

Name:

Photosynthesis

Title:

Crystal structure of a rod form of c-phycocyanin from themosynechococcus vulcanus at 1.5 angstroms

Structure:

C-phycocyanin alpha subunit. Chain: a. C-phycocyanin beta subunit. Chain: b

Source:

Thermosynechococcus vulcanus. Synechococcus vulcanus. Organism_taxid: 32053. Organism_taxid: 32053

Resolution:

1.50Å R-factor: 0.239 R-free: 0.263

Authors:

L.David,A.Marx,N.Adir

Key ref:

L.David et al. (2011). High-resolution crystal structures of trimeric and rod phycocyanin. J Mol Biol, 405, 201-213. PubMed id: 21035460

Date:

22-Jul-10 Release date: 03-Nov-10

Protein chain

Q9AM02  (Q9AM02_THEVL) -  C-phycocyanin alpha subunit (Fragment) from Thermostichus vulcanus

Seq: 162 a.a.

Struc: 162 a.a.

Protein chain

Q71RW8  (Q71RW8_THEVL) -  C-phycocyanin beta subunit (Fragment) from Thermostichus vulcanus

Seq: 172 a.a.

Struc: 172 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

J Mol Biol 405:201-213 (2011)

PubMed id: 21035460

High-resolution crystal structures of trimeric and rod phycocyanin.

L.David, A.Marx, N.Adir.

ABSTRACT

The phycobilisome light-harvesting antenna in cyanobacteria and red algae is assembled from two substructures: a central core composed of allophycocyanin surrounded by rods that always contain phycocyanin (PC). Unpigmented proteins called linkers are also found within the rods and core. We present here two new structures of PC from the thermophilic cyanobacterium Thermosynechococcus vulcanus. We have determined the structure of trimeric PC to 1.35 Å, the highest resolution reported to date for this protein. We also present a structure of PC isolated in its intact and functional rod form at 1.5 Å. Analysis of rod crystals showed that in addition to the α and β PC subunit, there were three linker proteins: the capping rod linker (L(R)(8.7)), the rod linker (L(R)), and only one of three rod-core linkers (L(RC), CpcG4) with a stoichiometry of 12:12:1:1:1. This ratio indicates that the crystals contained rods composed of two hexamers. The crystallographic parameters of the rod crystals are nearly identical with that of the trimeric form, indicating that the linkers do not affect crystal packing and are completely embedded within the rod cavities. Absorption and fluorescence emission spectra were red-shifted, as expected for assembled rods, and this could be shown for the rod in solution as well as in crystal using confocal fluorescence microscopy. The crystal packing imparts superimposition of the three rod linkers, canceling out their electron density. However, analysis of B-factors and the conformations of residues facing the rod channel indicate the presence of linkers. Based on the experimental evidence presented here and a homology-based model of the L(R) protein, we suggest that the linkers do not in fact link between rod hexamers but stabilize the hexameric assembly and modify rod energy absorption and transfer capabilities.