2C8K: Crystal Structure Of (Sr) Calcium-Atpase E2(Tg) With Partially Occupied Amppcp Site

We present crystal structures of the calcium-free E2 state of the sarcoplasmic reticulum Ca2+ -ATPase, stabilized by the inhibitor thapsigargin and the ATP analog AMPPCP. The structures allow us to describe the ATP binding site in a modulatory mode uncoupled from the Asp351 phosphorylation site. The Glu439 side chain interacts with AMPPCP via an Mg2+ ion in accordance with previous Fe2+ -cleavage studies implicating this residue in the ATPase cycle and in magnesium binding. Functional data on Ca2+ mediated activation indicate that the crystallized state represents an initial stage of ATP modulated deprotonation of E2, preceding the binding of Ca2+ ions in the membrane from the cytoplasmic side. We propose a mechanism of Ca2+ activation of phosphorylation leading directly from the compact E2-ATP form to the Ca2E1-ATP state. In addition, a role of Glu439 in ATP modulation of other steps of the functional cycle is suggested.
PDB ID: 2C8KDownload
MMDB ID: 39629
PDB Deposition Date: 2005/12/6
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 2.8  Å
Source Organism:
Similar Structures:
Biological Unit for 2C8K: monomeric; determined by author and by software (PQS)
Molecular Components in 2C8K
Label Count Molecule
Protein (1 molecule)
Arcoplasmic/endoplasmic Reticulum Calcium Atpase 1(Gene symbol: ATP2A1)
Molecule annotation
Chemicals (4 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB