1uhh
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(New page: 200px<br /><applet load="1uhh" size="450" color="white" frame="true" align="right" spinBox="true" caption="1uhh, resolution 1.80Å" /> '''Crystal structure of...)
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Revision as of 02:00, 21 November 2007
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Crystal structure of cp-aequorin
Overview
The photoprotein aequorin emits light by an intramolecular reaction in the, presence of a trace amount of Ca(2+). Semi-synthetic aequorins, produced, by replacing the coelenterazine moiety in aequorin with the analogues of, coelenterazine, show widely different sensitivities to Ca(2+). To, understand the structural basis of the Ca(2+)-sensitivity, we determined, the crystal structures of four semi-synthetic aequorins (cp-, i-, br- and, n-aequorins) at resolutions of 1.6-1.8 A. In general, the protein, structures of these semi-synthetic aequorins are almost identical to, native aequorin. Of the four EF-hand domains in the molecule, EF-hand II, does not bind Ca(2+), and the loop of EF-hand IV is clearly deformed. It, is most likely that the binding of Ca(2+) with EF-hands I and III triggers, luminescence. Although little difference was found in the overall, structures of aequorins investigated, some significant differences were, found in the interactions between the substituents of coelenterazine, moiety and the amino acid residues in the binding pocket. The, coelenterazine moieties in i-, br-, and n-aequorins have bulky, 2-substitutions, which can interfere with the conformational changes of, protein structure that follow the binding of Ca(2+) to aequorin. In, cp-aequorin, the cyclopentylmethyl group that substitutes for the original, 8-benzyl group does not interact hydrophobically with the protein part, giving the coelenterazine moiety more conformational freedom to promote, the light-emitting reaction. The differences of various semi-synthetic, aequorins in Ca(2+)-sensitivity and reaction rate are explained by the, capability of the involved groups and structures to undergo conformational, changes in response to the Ca(2+)-binding.
About this Structure
1UHH is a Single protein structure of sequence from Aequorea victoria with CZP as ligand. Full crystallographic information is available from OCA.
Reference
The crystal structures of semi-synthetic aequorins., Toma S, Chong KT, Nakagawa A, Teranishi K, Inouye S, Shimomura O, Protein Sci. 2005 Feb;14(2):409-16. Epub 2005 Jan 4. PMID:15632284
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