RCSB PDB - 7M5M: PCNA bound to peptide mimetic

 7M5M

PCNA bound to peptide mimetic


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.00 Å
  • R-Value Free: 0.274 
  • R-Value Work: 0.240 
  • R-Value Observed: 0.242 

Starting Model: experimental
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Ligand Structure Quality Assessment 

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This is version 1.3 of the entry. See complete history


Literature

A cell permeable bimane-constrained PCNA-interacting peptide.

Horsfall, A.J.Vandborg, B.A.Kikhtyak, Z.Scanlon, D.B.Tilley, W.D.Hickey, T.E.Bruning, J.B.Abell, A.D.

(2021) RSC Chem Biol 2: 1499-1508

  • DOI: https://doi.org/10.1039/d1cb00113b
  • Primary Citation of Related Structures:  
    7M5L, 7M5M, 7M5N

  • PubMed Abstract: 

    The human sliding clamp protein known as proliferating cell nuclear antigen (PCNA) orchestrates DNA-replication and -repair and as such is an ideal therapeutic target for proliferative diseases, including cancer. Peptides derived from the human p21 protein bind PCNA with high affinity via a 3 10 -helical binding conformation and are known to shut down DNA-replication. Here, we present studies on short analogues of p21 peptides (143-151) conformationally constrained with a covalent linker between i , i + 4 separated cysteine residues at positions 145 and 149 to access peptidomimetics that target PCNA. The resulting macrocycles bind PCNA with K D values ranging from 570 nM to 3.86 μM, with the bimane-constrained peptide 7 proving the most potent. Subsequent X-ray crystallography and computational modelling studies of the macrocyclic peptides bound to PCNA indicated only the high-affinity peptide 7 adopted the classical 3 10 -helical binding conformation. This suggests the 3 10 -helical conformation is critical to high affinity PCNA binding, however NMR secondary shift analysis of peptide 7 revealed this secondary structure was not well-defined in solution. Peptide 7 is cell permeable and localised to the cell cytosol of breast cancer cells (MDA-MB-468), revealed by confocal microscopy showing blue fluorescence of the bimane linker. The inherent fluorescence of the bimane moiety present in peptide 7 allowed it to be directly imaged in the cell uptake assay, without attachment of an auxiliary fluorescent tag. This highlights a significant benefit of using a bimane constraint to access conformationally constrained macrocyclic peptides. This study identifies a small peptidomimetic that binds PCNA with higher affinity than previous reported p21 macrocycles, and is cell permeable, providing a significant advance toward development of a PCNA inhibitor for therapeutic applications.


  • Organizational Affiliation

    Institute of Photonics and Advanced Sensing (IPAS), The University of Adelaide Adelaide South Australia 5005 Australia john.bruning@adelaide.edu.au andrew.abell@adelaide.edu.au.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Proliferating cell nuclear antigen
A, B, C
259Homo sapiensMutation(s): 0 
Gene Names: PCNA
UniProt & NIH Common Fund Data Resources
Find proteins for P12004 (Homo sapiens)
Explore P12004 
Go to UniProtKB:  P12004
PHAROS:  P12004
GTEx:  ENSG00000132646 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP12004
Sequence Annotations
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  • Reference Sequence

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Entity ID: 2
MoleculeChains Sequence LengthOrganismDetailsImage
Peptide mimetic (ACE)RQCSMTCFYHSK(NH2) with linker
D, E
14synthetic constructMutation(s): 0 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
Sequence Annotations
Expand
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.00 Å
  • R-Value Free: 0.274 
  • R-Value Work: 0.240 
  • R-Value Observed: 0.242 
  • Space Group: P 31 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 83.579α = 90
b = 83.579β = 90
c = 187.494γ = 120
Software Package:
Software NamePurpose
PHENIXrefinement
Aimlessdata scaling
PDB_EXTRACTdata extraction
XDSdata reduction
PHASERphasing

Structure Validation

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Ligand Structure Quality Assessment 

Created with Raphaël 2.3.0Worse 01 BetterLigand structure goodness of fit to experimental dataBest fitted NBUClick on this verticalbar to view details

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2021-08-11
    Type: Initial release
  • Version 1.1: 2021-11-10
    Changes: Database references
  • Version 1.2: 2023-10-18
    Changes: Data collection, Refinement description
  • Version 1.3: 2024-11-13
    Changes: Structure summary