Cyclin box structure of the P-TEFb subunit Cyclin T1 derived from a fusion complex with EIAV Tat

Experimental Data Snapshot

  • Resolution: 2.67 Å
  • R-Value Free: 0.306 
  • R-Value Work: 0.274 
  • R-Value Observed: 0.272 

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Cyclin Box Structure of the P-TEFb Subunit Cyclin T1 Derived from a Fusion Complex with EIAV Tat.

Anand, K.Schulte, A.Fujinaga, K.Scheffzek, K.Geyer, M.

(2007) J Mol Biol 370: 826-836

  • DOI: https://doi.org/10.1016/j.jmb.2007.04.077
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    The positive transcription elongation factor b (P-TEFb) is an essential regulator of viral gene expression during the life cycle of human immunodeficiency virus type 1 (HIV-1). Its cyclin T1 subunit forms a ternary complex with the viral transcriptional transactivator (Tat) protein and the transactivation response (TAR) RNA element thereby activating cyclin dependent kinase 9 (Cdk9), which stimulates transcription at the level of chain elongation. We report the structure of the cyclin box domain of human cyclin T1 at a resolution of 2.67 A. The structure was obtained by crystallographic analysis of a fusion protein composed of cyclin T1 linked to the transactivator protein Tat from equine infectious anemia virus (EIAV), which is functionally and structurally related to HIV-1 Tat. The conserved cyclin box domain of cyclin T1 exhibits structural features for interaction with physiological binding partners such as Cdk9. A recognition site for Cdk/Cyclin substrates is partly covered by a cyclin T-specific insert, suggesting specific interactions with regulatory factors. The previously identified Tat/TAR recognition motif (TRM) forms a C-terminal helix that is partly occluded in the cyclin box repeat interface, while cysteine 261 is accessible to form an intermolecular zinc finger with Tat. Residues of the TRM contribute to a positively charged groove that may directly attract RNA molecules. The EIAV Tat protein instead appeared undefined from the electron density map suggesting that it is highly disordered. Functional experiments confirmed the TAR binding properties of the fusion protein and suggested residues on the second cyclin box repeat to contribute to Tat stimulated transcription.

  • Organizational Affiliation

    EMBL Heidelberg, Structural and Computational Biology & Developmental Biology Unit, 69117 Heidelberg, Germany.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Cyclin-T1, Protein Tat
A, B, C, D
358Homo sapiensEquine infectious anemia virus
This entity is chimeric
Mutation(s): 0 
Gene Names: CCNT1
UniProt & NIH Common Fund Data Resources
Find proteins for O60563 (Homo sapiens)
Explore O60563 
Go to UniProtKB:  O60563
PHAROS:  O60563
Find proteins for P32544 (Equine infectious anemia virus (isolate CL22))
Explore P32544 
Go to UniProtKB:  P32544
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupsP32544O60563
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.67 Å
  • R-Value Free: 0.306 
  • R-Value Work: 0.274 
  • R-Value Observed: 0.272 
  • Space Group: H 3
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 203.83α = 90
b = 203.83β = 90
c = 124.79γ = 120
Software Package:
Software NamePurpose
ADSCdata collection
XDSdata reduction
XSCALEdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2007-07-03
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2017-07-26
    Changes: Refinement description, Source and taxonomy