1s36

Crystal structure of a Ca2+-discharged photoprotein: Implications for the mechanisms of the calcium trigger and the bioluminescence

spinqualitylabelsall models 1s36, resolution 1.96Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1s36 is a 1 chain structure with sequence from Black sea hydrozoan. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CEI, CL, GOL, NA Related: 1el4, 1ej3, 1jf0, 1jf2, 1qv0, 1qv1 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT, TOPSAN Function [OBL_OBELO] Ca(2+)-dependent bioluminescence photoprotein. Displays an emission peak at 470 nm (blue light). Trace amounts of calcium ion trigger the intramolecular oxidation of the chromophore, coelenterazine into coelenteramide and CO(2) with the concomitant emission of light. 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 Ca2+-regulated photoproteins are members of the EF-hand calcium-binding protein family. The addition of Ca2+ produces a blue bioluminescence by triggering a decarboxylation reaction of protein-bound hydroperoxycoelenterazine to form the product, coelenteramide, in an excited state. Based on the spatial structures of aequorin and several obelins, we have postulated mechanisms for the Ca2+ trigger and for generation of the different excited states that are the origin of the different colors of bioluminescence. Here we report the crystal structure of the Ca2+-discharged photoprotein obelin at 1.96-A resolution. The results lend support to the proposed mechanisms and provide new structural insight into details of these processes. Global conformational changes caused by Ca2+ association are typical of the class of calcium signal modulators within the EF-hand protein superfamily. Accommodation of the Ca2+ ions into the loops of the EF-hands is seen to propagate into the active site of the protein now occupied by the coelenteramide where there is a significant repositioning and flipping of the His-175 imidazole ring as crucially required in the trigger hypothesis. Also the H-bonding between His-22 and the coelenterazine found in the active photoprotein is preserved at the equivalent position of coelenteramide, confirming the proposed rapid excited state proton transfer that would lead to the excited state of the phenolate ion pair, which is responsible for the blue emission of bioluminescence. Crystal structure of a Ca2+-discharged photoprotein: implications for mechanisms of the calcium trigger and bioluminescence.,Deng L, Markova SV, Vysotski ES, Liu ZJ, Lee J, Rose J, Wang BC J Biol Chem. 2004 Aug 6;279(32):33647-52. Epub 2004 May 20. PMID:15155735 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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