2sas
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(New page: 200px<br /><applet load="2sas" size="450" color="white" frame="true" align="right" spinBox="true" caption="2sas, resolution 2.4Å" /> '''STRUCTURE OF A SARCOP...)
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Revision as of 11:53, 21 November 2007
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STRUCTURE OF A SARCOPLASMIC CALCIUM-BINDING PROTEIN FROM AMPHIOXUS REFINED AT 2.4 ANGSTROMS RESOLUTION
Overview
The three-dimensional structure of a sarcoplasmic Ca(2+)-binding protein, from the protochordate amphioxus has been determined at 2.4 A resolution, using multiple-isomorphous-replacement techniques. The refined model, includes all 185 residues, three calcium ions, and one water molecule. The, final crystallographic R-factor is 0.199. Bond lengths and bond angles in, the molecules have root-mean-square deviations from ideal values of 0.015, A and 2.8 degrees, respectively. The overall structure is highly compact, and globular with a predominantly hydrophobic core, unlike the extended, dumbbell-shaped structures of calmodulin or troponin C. There are four, distinct domains with the typical helix-loop-helix Ca(2+)-binding motif, (EF hand). The conformation of the pair of EF hands in the N-terminal half, of the protein is unusual due to the presence of an aspartate residue in, the twelfth position of the first Ca(2+)-binding loop, rather than the, usual glutamate. The C-terminal half of the molecule contains one, Ca(2+)-binding domain with a novel helix-loop-helix conformation and one, Ca(2+)-binding domain that is no longer functional because of amino acid, changes. The overall structure is quite similar to a sarcoplasmic, Ca(2+)-binding protein from sandworm, although there is only about 12%, amino acid sequence identity between them. The similarity of the, structures of these two proteins suggests that all sarcoplasmic, Ca(2+)-binding proteins will have the same general conformation, even, though there is very little conservation of primary structure among the, proteins from various species.
About this Structure
2SAS is a Single protein structure of sequence from Branchiostoma lanceolatum with CA as ligand. Full crystallographic information is available from OCA.
Reference
Structure of a sarcoplasmic calcium-binding protein from amphioxus refined at 2.4 A resolution., Cook WJ, Jeffrey LC, Cox JA, Vijay-Kumar S, J Mol Biol. 1993 Jan 20;229(2):461-71. PMID:8429557
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