The crystal structure of the human DNA polymerase delta processivity factor PCNA (proliferating cell nuclear antigen) complexed with a 22 residue peptide derived from the C-terminus of the cell-cycle checkpoint protein p21(WAF1/CIP1) has been determined at 2.6 angstrom resolution. p21 binds to PCNA in a 1:1 stoichiometry with an extensive array of interactions that include the formation of a beta sheet with the interdomain connector loop of PCNA. An intact trimeric ring is maintained in the structure of the p21-PCNA complex, with a central hole available for DNA interaction. The ability of p21 to inhibit the action of PCNA is therefore likely to be due to its masking of elements on PCNA that are required for the binding of other components of the polymerase assembly.
PDB ID: 1AXCDownload
MMDB ID: 7100
PDB Deposition Date: 1997/10/14
Updated in MMDB: 1998/11
Experimental Method:
x-ray diffraction
Resolution: 2.6  Å
Source Organism:
Similar Structures:
Biological Unit for 1AXC: hexameric; determined by author and by software (PISA)
Molecular Components in 1AXC
Label Count Molecule
Proteins (6 molecules)
Pcna(Gene symbol: PCNA)
Molecule annotation
P21/waf1(Gene symbol: CDKN1A)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB