Experimental Data Snapshot

  • Resolution: 1.95 Å
  • R-Value Free: 0.211 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.195 

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Archaeal Sm proteins form heptameric and hexameric complexes: crystal structures of the Sm1 and Sm2 proteins from the hyperthermophile Archaeoglobus fulgidus.

Toro, I.Basquin, J.Teo-Dreher, H.Suck, D.

(2002) J Mol Biol 320: 129-142

  • DOI: https://doi.org/10.1016/S0022-2836(02)00406-0
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Proteins of largely unknown function related to the Sm proteins present in the core domain of eukaryotic small nuclear ribonucleoprotein particles have recently been detected in Archaea. In contrast to eukaryotes, Archaea contain maximally two distinct Sm-related proteins belonging to different subfamilies, we refer to as Sm1 and Sm2. Here we report the crystal structures of the Sm1- and Sm2-type proteins from the hyperthermophilic euryarchaeon Archaeoglobus fulgidus (AF-Sm1 and AF-Sm2) at a resolution of 2.5 and 1.95 A, respectively. While the AF-Sm1 protein forms a heptameric ring structure similar to that found in other archaeal Sm1-type proteins, the AF-Sm2 protein unexpectedly forms a homo-hexamer in the crystals, and, as is evident from the mass spectrometric analysis, also in solution. Both proteins have essentially the same monomer fold and inter-subunit beta-sheet hydrogen bonding giving rise to a similar overall architecture of the doughnut-shaped six and seven-membered rings. In addition, a conserved uracil-binding pocket identified previously in an AF-Sm1/RNA complex, suggests a common RNA-binding mode for the AF-Sm1 and AF-Sm2 proteins, in line with solution studies showing preferential binding to U-rich oligonucleotides for both proteins. Clear differences are however seen in the charge distribution within the two structures. The rough faces of the rings, i.e. the faces not containing the base binding pockets, have opposite charges in the two structures, being predominantly positive in AF-Sm1 and negative in AF-Sm2. Differences in the ionic interactions between subunits provide an explanation for the distinctly different oligomerisation behaviour of the AF-Sm1 and AF-Sm2 proteins and of Sm1- and Sm2-type proteins in general, as well as the stability of their complexes. Implications for the functions of archaeal Sm proteins are being discussed.

  • Organizational Affiliation

    Structural and Computational Biology Programme, EMBL, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Archaeal Sm-like protein AF-Sm277Archaeoglobus fulgidusMutation(s): 0 
Gene Names: AF0362
Find proteins for O29885 (Archaeoglobus fulgidus (strain ATCC 49558 / DSM 4304 / JCM 9628 / NBRC 100126 / VC-16))
Explore O29885 
Go to UniProtKB:  O29885
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupO29885
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.95 Å
  • R-Value Free: 0.211 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.195 
  • Space Group: P 6
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 58.42α = 90
b = 58.42β = 90
c = 32.084γ = 120
Software Package:
Software NamePurpose
MAR345data collection
XDSdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2002-07-03
    Type: Initial release
  • Version 1.1: 2008-04-28
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Derived calculations, Version format compliance
  • Version 1.3: 2017-10-11
    Changes: Refinement description
  • Version 1.4: 2024-02-14
    Changes: Data collection, Database references, Derived calculations
  • Version 1.5: 2024-04-03
    Changes: Refinement description