1KJU

Ca2+-ATPase in the E2 State


Experimental Data Snapshot

  • Method: ELECTRON MICROSCOPY
  • Resolution: 6 Å
  • Aggregation State: HELICAL ARRAY 
  • Reconstruction Method: HELICAL 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

A structural model for the catalytic cycle of Ca(2+)-ATPase.

Xu, C.Rice, W.J.He, W.Stokes, D.L.

(2002) J.Mol.Biol. 316: 201-211

  • DOI: 10.1006/jmbi.2001.5330

  • PubMed Abstract: 
  • Ca(2+)-ATPase is responsible for active transport of calcium ions across the sarcoplasmic reticulum membrane. This coupling involves an ordered sequence of reversible reactions occurring alternately at the ATP site within the cytoplasmic domains, or ...

    Ca(2+)-ATPase is responsible for active transport of calcium ions across the sarcoplasmic reticulum membrane. This coupling involves an ordered sequence of reversible reactions occurring alternately at the ATP site within the cytoplasmic domains, or at the calcium transport sites within the transmembrane domain. These two sites are separated by a large distance and conformational changes have long been postulated to play an important role in their coordination. To characterize the nature of these conformational changes, we have built atomic models for two reaction intermediates and postulated the mechanisms governing the large structural changes. One model is based on fitting the X-ray crystallographic structure of Ca(2+)-ATPase in the E1 state to a new 6 A structure by cryoelectron microscopy in the E2 state. This fit indicates that calcium binding induces enormous movements of all three cytoplasmic domains as well as significant changes in several transmembrane helices. We found that fluorescein isothiocyanate displaced a decavanadate molecule normally located at the intersection of the three cytoplasmic domains, but did not affect their juxtaposition; this result indicates that our model likely reflects a native E2 conformation and not an artifact of decavanadate binding. To explain the dramatic structural effect of calcium binding, we propose that M4 and M5 transmembrane helices are responsive to calcium binding and directly induce rotation of the phosphorylation domain. Furthermore, we hypothesize that both the nucleotide-binding and beta-sheet domains are highly mobile and driven by Brownian motion to elicit phosphoenzyme formation and calcium transport, respectively. If so, the reaction cycle of Ca(2+)-ATPase would have elements of a Brownian ratchet, where the chemical reactions of ATP hydrolysis are used to direct the random thermal oscillations of an innately flexible molecule.


    Related Citations: 
    • Crystal Structure of the Calcium Pump of Sarcoplasmic Reticulum at 2.6 A Resolution
      Toyoshima, C.,Nakasako, M.,Nomura, H.,Ogawa, H.
      (2000) Nature 405: 647
    • Modeling a Dehalogenase Fold into the 8-A Density Map for Ca(2+)-ATPase Defines a New Domain Structure
      Stokes, D.L.,Green, N.M.
      (2000) Biophys.J. 78: 1765
    • Structure of the Calcium Pump from Sarcoplasmic Reticulum at 8-A Resolution
      Zhang, P.,Toyoshima, C.,Yonekura, K.,Green, N.M.,Stokes, D.L.
      (1998) Nature 392: 835
    • Distortion Correction of Tubular Crystals: Improvements in the Acetylcholine Receptor Structure
      Beroukhim, R.,Unwin, N.
      (1997) Ultramicroscopy 70: 57


    Organizational Affiliation

    Skirball Institute for Biomolecular Medicine, Department of Cell Biology, New York University School of Medicine, 540 First Ave, New York, NY, 10016, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Sarcoplasmic/endoplasmic reticulum calcium ATPase 1a
A
994Oryctolagus cuniculusGene Names: ATP2A1
EC: 3.6.3.8
Find proteins for P04191 (Oryctolagus cuniculus)
Go to Gene View: ATP2A1
Go to UniProtKB:  P04191
Experimental Data & Validation

Experimental Data

  • Method: ELECTRON MICROSCOPY
  • Resolution: 6 Å
  • Aggregation State: HELICAL ARRAY 
  • Reconstruction Method: HELICAL 

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2001-12-19
    Type: Initial release
  • Version 1.1: 2008-04-27
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance