PDBsum entry 2sas

Calcium-binding protein

PDB id: 2sas

Contents

Protein chain

185 a.a. *

Metals

_CA ×3

Waters ×1

* Residue conservation analysis

PDB id:

2sas

Name:

Calcium-binding protein

Title:

Structure of a sarcoplasmic calcium-binding protein from amphioxus refined at 2.4 angstroms resolution

Structure:

Sarcoplasmic calcium-binding protein. Chain: a. Engineered: yes

Source:

Branchiostoma lanceolatum. Amphioxus. Organism_taxid: 7740

Biol. unit:

Dimer (from PQS)

Resolution:

2.40Å R-factor: 0.199

Authors:

W.J.Cook,Y.S.Babu,J.A.Cox

Key ref:

W.J.Cook et al. (1993). Structure of a sarcoplasmic calcium-binding protein from amphioxus refined at 2.4 A resolution. J Mol Biol, 229, 461-471. PubMed id: 8429557

Date:

30-Jul-93 Release date: 31-Oct-93

Protein chain

P04570  (SCP2_BRALA) -  Sarcoplasmic calcium-binding proteins II, V, VI, and VII from Branchiostoma lanceolatum

Seq: 185 a.a.

Struc: 185 a.a.

J Mol Biol 229:461-471 (1993)

PubMed id: 8429557

Structure of a sarcoplasmic calcium-binding protein from amphioxus refined at 2.4 A resolution.

W.J.Cook, L.C.Jeffrey, J.A.Cox, S.Vijay-Kumar.

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.