Experimental Data Snapshot

  • Resolution: 3.00 Å
  • R-Value Free: 0.263 
  • R-Value Work: 0.203 
  • R-Value Observed: 0.203 

wwPDB Validation   3D Report Full Report

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The L3 loop and C-terminal phosphorylation jointly define Smad protein trimerization.

Chacko, B.M.Qin, B.Correia, J.J.Lam, S.S.de Caestecker, M.P.Lin, K.

(2001) Nat Struct Biol 8: 248-253

  • DOI: https://doi.org/10.1038/84995
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Smad proteins mediate the transforming growth factor beta responses. C-terminal phosphorylation of R-Smads leads to the recruitment of Smad4 and the formation of active signaling complexes. We investigated the mechanism of phosphorylation-induced Smad complex formation with an activating pseudo-phosphorylated Smad3. Pseudo-phosphorylated Smad3 has a greater propensity to homotrimerize, and recruits Smad4 to form a heterotrimer containing two Smad3 and one Smad4. The trimeric interaction is mediated through conserved interfaces to which tumorigenic mutations map. Furthermore, a conserved Arg residue within the L3 loop, located near the C-terminal phosphorylation sites of the neighboring subunit, is essential for trimerization. We propose that the phosphorylated C-terminal residues interact with the L3 loop of the neighboring subunit to stabilize the trimer interaction.

  • Organizational Affiliation

    Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 55 Lake Ave. North, Worcester, Massachusetts 01655, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B, C
268Homo sapiensMutation(s): 1 
UniProt & NIH Common Fund Data Resources
Find proteins for Q13485 (Homo sapiens)
Explore Q13485 
Go to UniProtKB:  Q13485
PHAROS:  Q13485
GTEx:  ENSG00000141646 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ13485
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 3.00 Å
  • R-Value Free: 0.263 
  • R-Value Work: 0.203 
  • R-Value Observed: 0.203 
  • Space Group: I 41 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 140.855α = 90
b = 140.855β = 90
c = 194.613γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
CCP4data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2000-11-29
    Type: Initial release
  • Version 1.1: 2008-04-27
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2021-10-27
    Changes: Database references
  • Version 1.4: 2024-02-07
    Changes: Data collection