2d1e
From Proteopedia
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Crystal structure of PcyA-biliverdin complex
Overview
Phytobilins (light harvesting and photoreceptor pigments in higher plants, algae, and cyanobacteria) are synthesized from biliverdin IXalpha (BV) by, ferredoxin-dependent bilin reductases (FDBRs). Phycocyanobilin:ferredoxin, oxidoreductase (PcyA), one such FDBR, is a new class of radical enzymes, that require neither cofactors nor metals and serially reduces the vinyl, group of the D-ring and A-ring of BV using four electrons from ferredoxin, to produce phycocyanobilin, one of the phytobilins. We have determined the, crystal structure of PcyA from Synechocystis sp. PCC 6803 in complex with, BV, revealing the first tertiary structure of an FDBR family member. PcyA, is folded in a three-layer alpha/beta/alpha sandwich structure, in which, BV in a cyclic conformation is positioned between the beta-sheet and, C-terminal alpha-helices. The basic patch on the PcyA surface near the BV, molecule may provide a binding site for acidic ferredoxin, allowing direct, transfer of electrons to BV. The orientation of BV is definitely fixed in, PcyA by several hydrophilic interactions and the shape of the BV binding, pocket of PcyA. We propose the mechanism by which the sequential reduction, of the D- and A-rings is controlled, where Asp-105, located between the, two reduction sites, would play the central role by changing its, conformation during the reaction. Homology modeling of other FDBRs based, on the PcyA structure fits well with previous genetic and biochemical, data, thereby providing a structural basis for the reaction mechanism of, FDBRs.
About this Structure
2D1E is a Single protein structure of sequence from Synechocystis sp. with NA and BLA as ligands. Active as Phycocyanobilin:ferredoxin oxidoreductase, with EC number 1.3.7.5 Full crystallographic information is available from OCA.
Reference
Crystal structure of phycocyanobilin:ferredoxin oxidoreductase in complex with biliverdin IXalpha, a key enzyme in the biosynthesis of phycocyanobilin., Hagiwara Y, Sugishima M, Takahashi Y, Fukuyama K, Proc Natl Acad Sci U S A. 2006 Jan 3;103(1):27-32. Epub 2005 Dec 27. PMID:16380422
Page seeded by OCA on Wed Nov 21 09:23:11 2007
