2v08

Structure of wild-type Phormidium laminosum cytochrome c6

spinqualitylabelsall models 2v08, resolution 2.00Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2v08 is a 2 chain structure with sequence from Phormidium laminosum. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2Å Ligands: CL, HEC, IMD, ZN Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function CYC6_PARLV Functions as an electron carrier between membrane-bound cytochrome b6-f and photosystem I in oxygenic photosynthesis. 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 Cytochrome c6A is a unique dithio-cytochrome of green algae and plants. It has a very similar core structure to that of bacterial and algal cytochromes c6 but is unable to fulfill the same function of transferring electrons from cytochrome f to photosystem I. A key feature is that its heme midpoint potential is more than 200 mV below that of cytochrome c6 despite having His and Met as axial heme-iron ligands. To identify the molecular origins of the difference in potential, the structure of cytochrome c6 from the cyanobacterium Phormidium laminosum has been determined by X-ray crystallography and compared with the known structure of cytochrome c6A. One salient difference of the heme pockets is that a highly conserved Gln (Q51) in cytochrome c6 is replaced by Val (V52) in c6A. Using protein film voltammetry, we found that swapping these residues raised the c6A potential by +109 mV and decreased that of c6 by almost the same extent, -100 mV. X-ray crystallography of the V52Q protein showed that the Gln residue adopts the same configuration relative to the heme as in cytochrome c6 and we propose that this stereochemistry destabilizes the oxidized form of the heme. Consequently, replacement of Gln by Val was probably a key step in the evolution of cytochrome c6A from cytochrome c6, inhibiting reduction by the cytochrome b6f complex and facilitating establishment of a new function. Modulation of heme redox potential in the cytochrome c6 family.,Worrall JA, Schlarb-Ridley BG, Reda T, Marcaida MJ, Moorlen RJ, Wastl J, Hirst J, Bendall DS, Luisi BF, Howe CJ J Am Chem Soc. 2007 Aug 1;129(30):9468-75. Epub 2007 Jul 11. PMID:17625855 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Cytochrome f 3D structures

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