1s36

From Proteopedia

---

Revision as of 23:56, 20 November 2007

proteopedia linkproteopedia link

spinqualitylabelsall models 1s36, resolution 1.96Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

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

Overview

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.

About this Structure

1S36 is a Single protein structure of sequence from Obelia longissima with NA, CL, CEI and GOL as ligands. Full crystallographic information is available from OCA.

Reference

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

Page seeded by OCA on Wed Nov 21 02:03:58 2007