Structure of the Arl6 BBS3 Small GTPase from Trypanosoma brucei with bound nucleotide analogue GppNp

Experimental Data Snapshot

  • Resolution: 2.00 Å
  • R-Value Free: 0.248 
  • R-Value Work: 0.183 
  • R-Value Observed: 0.187 

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Crystal Structure of the Small Gtpase Arl6/Bbs3 from Trypanosomabrucei.

Hemsworth, G.R.Price, H.P.Smith, D.F.Wilson, K.S.

(2013) Protein Sci 22: 196

  • DOI: https://doi.org/10.1002/pro.2198
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Arl6/BBS3 is a small GTPase, mutations in which are implicated in the human ciliopathy Bardet-Biedl Syndrome (BBS). Arl6 is proposed to facilitate the recruitment of a large protein complex known as the BBSome to the base of the primary cilium, mediating specific trafficking of molecules to this important sensory organelle. Orthologues of Arl6 and the BBSome core subunits have been identified in the genomes of trypanosomes. Flagellum function and motility are crucial to the survival of Trypanosoma brucei, the causative agent of human African sleeping sickness, in the human bloodstream stage of its lifecycle and so the function of the BBSome proteins in trypanosomes warrants further study. RNAi knockdown of T. brucei Arl6 (TbArl6) has recently been shown to result in shortening of the trypanosome flagellum. Here we present the crystal structure of TbArl6 with the bound non-hydrolysable GTP analog GppNp at 2.0 Å resolution and highlight important differences between the trypanosomal and human proteins. Analysis of the TbArl6 active site confirms that it lacks the key glutamine that activates the nucleophile during GTP hydrolysis in other small GTPases. Furthermore, the trypanosomal proteins are significantly shorter at their N-termini suggesting a different method of membrane insertion compared to humans. Finally, analysis of sequence conservation suggests two surface patches that may be important for protein-protein interactions. Our structural analysis thus provides the basis for future biochemical characterisation of this important family of small GTPases.

  • Organizational Affiliation

    Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York, United Kingdom.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
ADP-RIBOSYLATION FACTOR, PUTATIVE (SMALL GTPASE, PUTATIVE)199Trypanosoma brucei brucei TREU927Mutation(s): 0 
Find proteins for C9ZVV9 (Trypanosoma brucei gambiense (strain MHOM/CI/86/DAL972))
Explore C9ZVV9 
Go to UniProtKB:  C9ZVV9
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupC9ZVV9
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.00 Å
  • R-Value Free: 0.248 
  • R-Value Work: 0.183 
  • R-Value Observed: 0.187 
  • Space Group: P 32 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 70.92α = 90
b = 70.92β = 90
c = 80.928γ = 120
Software Package:
Software NamePurpose
XDSdata reduction
SCALAdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2012-12-12
    Type: Initial release
  • Version 1.1: 2013-02-13
    Changes: Database references