4EHQ

Crystal Structure of Calmodulin Binding Domain of Orai1 in Complex with Ca2+/Calmodulin Displays a Unique Binding Mode


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.90 Å
  • R-Value Free: 0.216 
  • R-Value Work: 0.179 
  • R-Value Observed: 0.181 

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Literature

Crystal structure of calmodulin binding domain of orai1 in complex with ca2+*calmodulin displays a unique binding mode.

Liu, Y.Zheng, X.Mueller, G.A.Sobhany, M.Derose, E.F.Zhang, Y.London, R.E.Birnbaumer, L.

(2012) J Biol Chem 287: 43030-43041

  • DOI: 10.1074/jbc.M112.380964
  • Primary Citation of Related Structures:  
    4EHQ

  • PubMed Abstract: 
  • Orai1 is a plasma membrane protein that in its tetrameric form is responsible for calcium influx from the extracellular environment into the cytosol in response to interaction with the Ca(2+)-depletion sensor STIM1. This is followed by a fast Ca(2+)·calmodulin (CaM)-dependent inhibition, resulting from CaM binding to an Orai1 region called the calmodulin binding domain (CMBD) ...

    Orai1 is a plasma membrane protein that in its tetrameric form is responsible for calcium influx from the extracellular environment into the cytosol in response to interaction with the Ca(2+)-depletion sensor STIM1. This is followed by a fast Ca(2+)·calmodulin (CaM)-dependent inhibition, resulting from CaM binding to an Orai1 region called the calmodulin binding domain (CMBD). The interaction between Orai1 and CaM at the atomic level remains unknown. Here, we report the crystal structure of a CaM·Orai1-CMBD complex showing one CMBD bound to the C-terminal lobe of CaM, differing from other CaM-target protein complexes, in which both N- and C-terminal lobes of CaM (CaM-N and CaM-C) are involved in target binding. Orai1-CMBD binds CaM-C mainly through hydrophobic interactions, primarily involving residue Trp(76) of Orai1-CMBD, which interacts with the hydrophobic pocket of CaM-C. However, NMR data, isothermal titration calorimetry data, and pulldown assays indicated that CaM-N and CaM-C both can bind Orai1-CMBD, with CaM-N having ∼4 times weaker affinity than CaM-C. Pulldown assays of a Orai1-CMBD(W76E) mutant, gel filtration chromatography data, and NOE signals indicated that CaM-N and CaM-C can each bind one Orai1-CMBD. Thus our studies support an unusual, extended 1:2 binding mode of CaM to Orai1-CMBDs, and quantify the affinity of Orai1 for CaM. We propose a two-step mechanism for CaM-dependent Orai1 inactivation initiated by binding of the C-lobe of CaM to the CMBD of one Orai1 followed by the binding of the N-lobe of CaM to the CMBD of a neighboring Orai1.


    Organizational Affiliation

    Laboratory of Neurobiology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA. liuy3@niehs.nih.gov



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
CalmodulinA148Rattus norvegicusMutation(s): 0 
Gene Names: 
Calm1CalmCamCam1Calm2Cam2CambCalm3Cam3Camc...
Calm1CalmCamCam1Calm2Cam2CambCalm3Cam3CamcCaMI

UniProt
Find proteins for P0DP29 (Rattus norvegicus)
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Go to UniProtKB:  P0DP29
Protein Feature View
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  • Reference Sequence
  • Find similar proteins by:  Sequence   |   Structure
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
Calcium release-activated calcium channel protein 1B [auth G]20Homo sapiensMutation(s): 0 
Gene Names: ORAI1CRACM1TMEM142A
UniProt & NIH Common Fund Data Resources
Find proteins for Q96D31 (Homo sapiens)
Explore Q96D31 
Go to UniProtKB:  Q96D31
PHAROS:  Q96D31
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.90 Å
  • R-Value Free: 0.216 
  • R-Value Work: 0.179 
  • R-Value Observed: 0.181 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 100.074α = 90
b = 24.709β = 100.1
c = 60.903γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
PHENIXmodel building
PHENIXrefinement
DENZOdata reduction
SCALEPACKdata scaling
PHENIXphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2012-11-07
    Type: Initial release
  • Version 1.1: 2012-11-14
    Changes: Database references
  • Version 1.2: 2013-01-02
    Changes: Database references