2SAS

STRUCTURE OF A SARCOPLASMIC CALCIUM-BINDING PROTEIN FROM AMPHIOXUS REFINED AT 2.4 ANGSTROMS RESOLUTION

Summary for 2SAS

• Entry DOI: 10.2210/pdb2sas/pdb
• Descriptor: SARCOPLASMIC CALCIUM-BINDING PROTEIN, CALCIUM ION (3 entities in total)
• Functional Keywords: calcium-binding protein
• Biological source: Branchiostoma lanceolatum (amphioxus)
• Total number of polymer chains: 1
• Total formula weight: 21428.10

Authors

Cook, W.J.,Babu, Y.S.,Cox, J.A. (deposition date: 1993-07-30, release date: 1993-10-31, Last modification date: 2024-10-23)

Primary citation

Cook, W.J.,Jeffrey, L.C.,Cox, J.A.,Vijay-Kumar, S.
Structure of a sarcoplasmic calcium-binding protein from amphioxus refined at 2.4 A resolution.
J.Mol.Biol., 229:461-471, 1993

PubMed Abstract: 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.

PubMed: 8429557
DOI: 10.1006/jmbi.1993.1046

Experimental method

X-RAY DIFFRACTION (2.4 Å)