Biological Assembly 1  

 3D View: Structure | Electron Density | Ligand Interaction

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 3-mer - A2B1 

Biological assembly 1 assigned by authors and generated by PISA (software)

Macromolecule Content

• Total Structure Weight: 40.96 kDa 
• Atom Count: 2922 
• Residue Count: 343 
• Unique protein chains: 2

4AQR

Crystal structure of calmodulin in complex with the regulatory domain of a plasma-membrane Ca2+-ATPase

• DOI: 10.2210/pdb4AQR/pdb

• Classification: CA-BINDING PROTEIN/HYDROLASE
• Organism(s): Arabidopsis thaliana
• Expression System: Escherichia coli
• Mutation(s): No 


• Deposited: 2012-04-19 Released: 2012-10-17 
• Deposition Author(s): Tidow, H., Poulsen, L.R., Andreeva, A., Hein, K.L., Palmgren, M.G., Nissen, P.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 1.95 Å
• R-Value Free: 0.247 
• R-Value Work: 0.216 
• R-Value Observed: 0.217 

Literature

A Bimodular Mechanism of Calcium Control in Eukaryotes

Tidow, H., Poulsen, L.R., Andreeva, A., Knudsen, M., Hein, K.L., Wiuf, C., Palmgren, M.G., Nissen, P.

(2012) Nature 491: 468

• PubMed: 23086147 
• DOI: 10.1038/nature11539
• Primary Citation of Related Structures:  
  4AQR


• PubMed Abstract: 
  

Calcium ions (Ca(2+)) have an important role as secondary messengers in numerous signal transduction processes, and cells invest much energy in controlling and maintaining a steep gradient between intracellular (∼0.1-micromolar) and extracellular (∼2-millimolar) Ca(2+) concentrations. Calmodulin-stimulated calcium pumps, which include the plasma-membrane Ca(2+)-ATPases (PMCAs), are key regulators of intracellular Ca(2+) in eukaryotes. They contain a unique amino- or carboxy-terminal regulatory domain responsible for autoinhibition, and binding of calcium-loaded calmodulin to this domain releases autoinhibition and activates the pump. However, the structural basis for the activation mechanism is unknown and a key remaining question is how calmodulin-mediated PMCA regulation can cover both basal Ca(2+) levels in the nanomolar range as well as micromolar-range Ca(2+) transients generated by cell stimulation. Here we present an integrated study combining the determination of the high-resolution crystal structure of a PMCA regulatory-domain/calmodulin complex with in vivo characterization and biochemical, biophysical and bioinformatics data that provide mechanistic insights into a two-step PMCA activation mechanism mediated by calcium-loaded calmodulin. The structure shows the entire PMCA regulatory domain and reveals an unexpected 2:1 stoichiometry with two calcium-loaded calmodulin molecules binding to different sites on a long helix. A multifaceted characterization of the role of both sites leads to a general structural model for calmodulin-mediated regulation of PMCAs that allows stringent, highly responsive control of intracellular calcium in eukaryotes, making it possible to maintain a stable, basal level at a threshold Ca(2+) concentration, where steep activation occurs.

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Organizational Affiliation: 

Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Aarhus University, Gustav Wieds Vej 10c, DK-8000 Aarhus C, Denmark.

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
CALMODULIN-7	A, B	149	Arabidopsis thaliana	Mutation(s): 0  Gene Names: CAM7, At3g43810, T28A8.100
Find proteins for P59220 (Arabidopsis thaliana) Explore P59220  Go to UniProtKB:  P59220

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
CALCIUM-TRANSPORTING ATPASE 8, PLASMA MEMBRANE-TYPE	D	57	Arabidopsis thaliana	Mutation(s): 0  Gene Names: ACA8, At5g57110, MUL3.5 EC: 3.6.3.8 (PDB Primary Data), 7.2.2.10 (UniProt)
Find proteins for Q9LF79 (Arabidopsis thaliana) Explore Q9LF79  Go to UniProtKB:  Q9LF79

Small Molecules

Ligands 1 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
CA	A, B	CALCIUM ION Ca BHPQYMZQTOCNFJ-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 1.95 Å
• R-Value Free: 0.247 
• R-Value Work: 0.216 
• R-Value Observed: 0.217 
• Space Group: P 4₁ 2₁ 2

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 71.251	α = 90
b = 71.251	β = 90
c = 163.279	γ = 90

Software Package:

Software Name	Purpose
PHENIX	refinement
XDS	data reduction
XDS	data scaling
PHASER	phasing

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2012-04-19 
• Released Date: 2012-10-17 
Deposition Author(s): Tidow, H., Poulsen, L.R., Andreeva, A., Hein, K.L., Palmgren, M.G., Nissen, P.

Revision History 

• Version 1.0: 2012-10-17
  Type: Initial release
  
• Version 1.1: 2012-11-07
  Changes: Database references
• Version 1.2: 2012-11-21
  Changes: Database references