2x9i

Structure of the Mutant D105N of Phycoerythrobilin Synthase PebS from the Cyanophage P-SSM2 in complex with bound substrate Biliverdin IXA

spinqualitylabelsall models 2x9i, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2x9i is a 4 chain structure with sequence from Prochlorococcus phage P-SSM2. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.2Å Ligands: BLA, SO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function PEBS_BPPRM Plays a role in phycoerythrobilin biosynthesis, the red pigment chromophore photosynthetically active biliproteins of the host cyanobacteria. Uses a four-electron reduction to carry out the reactions catalyzed by two enzymes (EC 1.3.7.2 and EC 1.3.7.3) in host. Publication Abstract from PubMed Phycoerythrobilin (PEB) is a pink-colored open-chain tetrapyrrole molecule found in the cyanobacterial light-harvesting phycobilisome. Within the phycobilisome, PEB is covalently bound via thioether bonds to conserved cysteine residues of the phycobiliprotein subunits. In cyanobacteria, biosynthesis of PEB proceeds via two subsequent two-electron reductions catalyzed by the ferredoxin-dependent bilin reductases (FDBR) PebA and PebB starting from the open-chain tetrapyrrole biliverdin IXalpha. Recently, a new member of the FDBR family was identified in the genome of a marine cyanophage. In contrast to the cyanobacterial enzymes, PEB-synthase (PebS) from cyanophage combines both two-electron reductions for PEB synthesis. Here we show that PebS acts via a substrate radical mechanism and that two conserved aspartate residues at position 105 and 206 are critical for stereospecific substrate protonation and conversion. Based on the crystal structures of both PebS variants and presented biochemical and biophysical data a mechanism for BV conversion to PEB is postulated and discussed with respect to other FDBR family members. Radical mechanism of cyanophage phycoerythrobilin synthase (PebS).,Busch AW, Reijerse EJ, Lubitz W, Hofmann E, Frankenberg-Dinkel N Biochem J. 2010 Nov 4. PMID:21050180 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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