Structure of human Hexim1 (delta stammer) coiled coil domain

Experimental Data Snapshot

  • Resolution: 2.10 Å
  • R-Value Free: 0.296 
  • R-Value Work: 0.236 
  • R-Value Observed: 0.239 

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Structure and Dynamics of a Stabilized Coiled-Coil Domain in the P-TEFb Regulator Hexim1.

Bigalke, J.M.Dames, S.A.Blankenfeldt, W.Grzesiek, S.Geyer, M.

(2011) J Mol Biol 414: 639-653

  • DOI: https://doi.org/10.1016/j.jmb.2011.10.022
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    The positive transcription elongation factor P-TEFb mediates the transition from transcription initiation to productive elongation by phosphorylation of the C-terminal domain of RNA polymerase II. P-TEFb is negatively regulated by the cellular protein Hexim1 (hexamethylene bisacetamide-inducible protein 1), which is highly conserved in higher eukaryotes. The C-terminal coiled-coil domain of Hexim1 recognizes the Cyclin T subunit of P-TEFb, whereas a central PYNT motif is required to inhibit the cyclin-dependent kinase Cdk9 by a yet unknown mechanism. Here, the crystal structure of the Cyclin T-binding domain (TBD) of human Hexim1 was determined at 2.1 Å resolution using a deletion mutant of three residues in its central stammer motif. The structure showed a continuous parallel coiled-coil domain of nine hepta-repeats with a preceding helix encompassing up to 15 residues. Two uncommon residues at heptad a positions in the N-terminal part of the coiled-coil structure, Lys284 and Tyr291, stabilize the preceding helix by a tight intermolecular hydrogen bond network with residues of the opposing chain. These interactions delineate a characteristic turn between both helices that is supposed to mediate binding to Cyclin T1. Stabilization of the coiled-coil domain by deletion of the stammer region was confirmed by NMR spectroscopic and backbone dynamic analyses analyzing wild-type TBD and three mutant variants. This study thus provides structural insights into the recognition of the regulator protein Hexim1 by P-TEFb and the modulation of coiled-coil dynamics by specific discontinuities.

  • Organizational Affiliation

    Max-Planck-Institut für molekulare Physiologie, Abteilung Physikalische Biochemie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Protein HEXIM1
A, B
104Homo sapiensMutation(s): 1 
UniProt & NIH Common Fund Data Resources
Find proteins for O94992 (Homo sapiens)
Explore O94992 
Go to UniProtKB:  O94992
PHAROS:  O94992
GTEx:  ENSG00000186834 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupO94992
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.10 Å
  • R-Value Free: 0.296 
  • R-Value Work: 0.236 
  • R-Value Observed: 0.239 
  • Space Group: I 4
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 70.77α = 90
b = 70.77β = 90
c = 90.96γ = 90
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: 2011-10-19
    Type: Initial release
  • Version 1.1: 2011-11-09
    Changes: Database references
  • Version 1.2: 2011-12-21
    Changes: Database references