Structure of p18INK4c (F92N)

Experimental Data Snapshot

  • Resolution: 2.00 Å
  • R-Value Free: 0.263 
  • R-Value Work: 0.237 
  • R-Value Observed: 0.240 

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Structure-based design of p18INK4c proteins with increased thermodynamic stability and cell cycle inhibitory activity

Venkataramani, R.N.MacLachlan, T.K.Chai, X.El-Deiry, W.S.Marmorstein, R.

(2002) J Biol Chem 277: 48827-48833

  • DOI: https://doi.org/10.1074/jbc.M208061200
  • Primary Citation of Related Structures:  
    1MX2, 1MX4, 1MX6

  • PubMed Abstract: 

    p18(INK4c) is a member of the INK4 family of proteins that regulate the G(1) to S cell cycle transition by binding to and inhibiting the pRb kinase activity of cyclin-dependent kinases 4 and 6. The p16(INK4a) member of the INK4 protein family is altered in a variety of cancers and structure-function studies of the INK4 proteins reveal that the vast majority of missense tumor-derived p16(INK4a) mutations reduce protein thermodynamic stability. Based on this observation, we used p18(INK4c) as a model to test the proposal that INK4 proteins with increased stability might have enhanced cell cycle inhibitory activity. Structure-based mutagenesis was used to prepare p18(INK4c) mutant proteins with a predicted increase in stability. Using this approach, we report the generation of three mutant p18(INK4C) proteins, F71N, F82Q, and F92N, with increased stability toward thermal denaturation of which the F71N mutant also showed an increased stability to chemical denaturation. The x-ray crystal structures of the F71N, F82Q, and F92N p18INK4C mutant proteins were determined to reveal the structural basis for their increased stability properties. Significantly, the F71N mutant also showed enhanced CDK6 interaction and cell cycle inhibitory activity in vivo, as measured using co-immunoprecipitation and transient transfection assays, respectively. These studies show that a structure-based approach to increase the thermodynamic stability of INK4 proteins can be exploited to prepare more biologically active molecules with potential applications for the development of molecules to treat p16(INK4a)-mediated cancers.

  • Organizational Affiliation

    The Wistar Institute, Philadelphia, Pennsylvania 19104, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Cyclin-dependent kinase 6 inhibitor
A, B
168Homo sapiensMutation(s): 1 
UniProt & NIH Common Fund Data Resources
Find proteins for P42773 (Homo sapiens)
Explore P42773 
Go to UniProtKB:  P42773
PHAROS:  P42773
GTEx:  ENSG00000123080 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP42773
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.00 Å
  • R-Value Free: 0.263 
  • R-Value Work: 0.237 
  • R-Value Observed: 0.240 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 55.005α = 90
b = 150.843β = 90
c = 40.574γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2002-10-16
    Type: Initial release
  • Version 1.1: 2008-04-28
    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: 2024-02-14
    Changes: Data collection, Refinement description