1IWO: Crystal Structure Of The Sr Ca2+-Atpase In The Absence Of Ca2+

Citation:
Abstract
In skeletal muscle, calcium ions are transported (pumped) against a concentration gradient from the cytoplasm into the sarcoplasmic reticulum, an intracellular organelle. This causes muscle cells to relax after cytosolic calcium increases during excitation. The Ca(2+) ATPase that carries out this pumping is a representative P-type ion-transporting ATPase. Here we describe the structure of this ion pump at 3.1 A resolution in a Ca(2+)-free (E2) state, and compare it with that determined previously for the Ca(2+)-bound (E1Ca(2+)) state. The structure of the enzyme stabilized by thapsigargin, a potent inhibitor, shows large conformation differences from that in E1Ca(2+). Three cytoplasmic domains gather to form a single headpiece, and six of the ten transmembrane helices exhibit large-scale rearrangements. These rearrangements ensure the release of calcium ions into the lumen of sarcoplasmic reticulum and, on the cytoplasmic side, create a pathway for entry of new calcium ions.
PDB ID: 1IWODownload
MMDB ID: 20376
PDB Deposition Date: 2002/5/26
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 3.1  Å
Source Organism:
Similar Structures:
Biological Unit for 1IWO: dimeric; determined by author
Molecular Components in 1IWO
Label Count Molecule
Proteins (2 molecules)
2
Sarcoplasmic/endoplasmic Reticulum Calcium Atpase 1(Gene symbol: ATP2A1)
Molecule annotation
Chemicals (2 molecules)
1
2
* Click molecule labels to explore molecular sequence information.

Citing MMDB
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