3f0m

Crystal structure of radical D105N Synechocystis sp. PcyA

spinqualitylabelsall models 3f0m, resolution 1.50Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3f0m is a 1 chain structure with sequence from Aphanocapsa sp. (strain n-1). Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: BLA, EDO Related: 3f0j, 3f0k, 3f0l Gene: pcyA, slr0116 (Aphanocapsa sp. (strain N-1)) Activity: Phycocyanobilin:ferredoxin oxidoreductase, with EC number 1.3.7.5 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [PCYA_SYNY3] Catalyzes the four-electron reduction of biliverdin IX-alpha (2-electron reduction at both the A and D rings); the reaction proceeds via an isolatable 2-electron intermediate, 181,182-dihydrobiliverdin (By similarity). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed Heme-derived linear tetrapyrroles (phytobilins) in phycobiliproteins and phytochromes perform critical light-harvesting and light-sensing roles in oxygenic photosynthetic organisms. A key enzyme in their biogenesis, phycocyanobilin:ferredoxin oxidoreductase (PcyA), catalyzes the overall four-electron reduction of biliverdin IXalpha to phycocyanobilin--the common chromophore precursor for both classes of biliproteins. This interconversion occurs via semireduced bilin radical intermediates that are profoundly stabilized by selected mutations of two critical catalytic residues, Asp105 and His88. To understand the structural basis for this stabilization and to gain insight into the overall catalytic mechanism, we report the high-resolution crystal structures of substrate-loaded Asp105Asn and His88Gln mutants of Synechocystis sp. PCC 6803 PcyA in the initial oxidized and one-electron reduced radical states. Unlike wild-type PcyA, both mutants possess a bilin-interacting axial water molecule that is ejected from the active site upon formation of the enzyme-bound neutral radical complex. Structural studies of both mutants also show that the side chain of Glu76 is unfavorably located for D-ring vinyl reduction. On the basis of these structures and companion (15)N-(1)H long-range HMQC NMR analyses to assess the protonation state of histidine residues, we propose a new mechanistic scheme for PcyA-mediated reduction of both vinyl groups of biliverdin wherein an axial water molecule, which prematurely binds and ejects from both mutants upon one electron reduction, is required for catalytic turnover of the semireduced state. Structural basis for hydration dynamics in radical stabilization of bilin reductase mutants.,Kohler AC, Gae DD, Richley MA, Stoll S, Gunn A, Lim S, Martin SS, Doukov TI, Britt RD, Ames JB, Lagarias JC, Fisher AJ Biochemistry. 2010 Jul 27;49(29):6206-18. PMID:20557110 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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