3N8G: Structure Of The (sr)ca2+-atpase Ca2-e1-caamppcp Form

Citation:
Abstract
The sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) is a transmembrane ion transporter belonging to the P(II)-type ATPase family. It performs the vital task of re-sequestering cytoplasmic Ca(2+) to the sarco/endoplasmic reticulum store, thereby also terminating Ca(2+)-induced signaling such as in muscle contraction. This minireview focuses on the transport pathways of Ca(2+) and H(+) ions across the lipid bilayer through SERCA. The ion-binding sites of SERCA are accessible from either the cytoplasm or the sarco/endoplasmic reticulum lumen, and the Ca(2+) entry and exit channels are both formed mainly by rearrangements of four N-terminal transmembrane alpha-helices. Recent improvements in the resolution of the crystal structures of rabbit SERCA1a have revealed a hydrated pathway in the C-terminal transmembrane region leading from the ion-binding sites to the cytosol. A comparison of different SERCA conformations reveals that this C-terminal pathway is exclusive to Ca(2+)-free E2 states, suggesting that it may play a functional role in proton release from the ion-binding sites. This is in agreement with molecular dynamics simulations and mutational studies and is in striking analogy to a similar pathway recently described for the related sodium pump. We therefore suggest a model for the ion exchange mechanism in P(II)-ATPases including not one, but two cytoplasmic pathways working in concert.
PDB ID: 3N8GDownload
MMDB ID: 91181
PDB Deposition Date: 2010/5/28
Updated in MMDB: 2011/06
Experimental Method:
x-ray diffraction
Resolution: 2.58  Å
Source Organism:
Similar Structures:
Biological Unit for 3N8G: monomeric; determined by author and by software (PISA)
Molecular Components in 3N8G
Label Count Molecule
Protein (1 molecule)
1
Sarcoplasmic/endoplasmic Reticulum Calcium Atpase 1 Isoform Serca 1A
Molecule annotation
Chemicals (5 molecules)
1
3
2
1
3
1
* Click molecule labels to explore molecular sequence information.

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