5ejx

X-ray Free Electron Laser Structure of Cytochrome C Peroxidase

spinqualitylabelsall models 5ejx, resolution 1.50Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 5ejx is a 1 chain structure with sequence from Baker's yeast. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: HEM, PO4 Related: 3m23, 3m25, 3m26, 3m27, 3m28, 3m29, 3m2a, 3m2b, 3m2c, 3m2d, 3m2e, 3m2f, 3m2g, 3m2h, 3m2i, 5ejt Gene: CCP1, CCP, CPO, YKR066C (Baker's yeast) Activity: Cytochrome-c peroxidase, with EC number 1.11.1.5 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [CCPR_YEAST] Destroys radicals which are normally produced within the cells and which are toxic to biological systems. Publication Abstract from PubMed The reaction of peroxides with peroxidases oxidizes the heme iron from Fe(III) to Fe(IV)=O and a porphyrin or aromatic side chain to a cationic radical. X-ray-generated hydrated electrons rapidly reduce Fe(IV), thereby requiring very short exposures using many crystals, and, even then, some reduction cannot be avoided. The new generation of X-ray free electron lasers capable of generating intense X-rays on the tenths of femtosecond time scale enables structure determination with no reduction or X-ray damage. Here, we report the 1.5-A crystal structure of cytochrome c peroxidase (CCP) compound I (CmpI) using data obtained with the Stanford Linear Coherent Light Source (LCLS). This structure is consistent with previous structures. Of particular importance is the active site water structure that can mediate the proton transfer reactions required for both CmpI formation and reduction of Fe(IV)=O to Fe(III)-OH. The structures indicate that a water molecule is ideally positioned to shuttle protons between an iron-linked oxygen and the active site catalytic His. We therefore have carried out both computational and kinetic studies to probe the reduction of Fe(IV)=O. Kinetic solvent isotope experiments show that the transfer of a single proton is critical in the peroxidase rate-limiting step, which is very likely the proton-coupled reduction of Fe(IV)=O to Fe(III)-OH. We also find that the pKa of the catalytic His substantially increases in CmpI, indicating that this active site His is the source of the proton required in the reduction of Fe(IV)=O to Fe(IV)-OH. Crystal structure of the pristine peroxidase ferryl center and its relevance to proton-coupled electron transfer.,Chreifi G, Baxter EL, Doukov T, Cohen AE, McPhillips SE, Song J, Meharenna YT, Soltis SM, Poulos TL Proc Natl Acad Sci U S A. 2016 Jan 19. pii: 201521664. PMID:26787871 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Cytochrome c peroxidase 3D structures

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