p53 is a human tumor suppressor protein encoded by the TP53 gene. 

Crystal structure of four p53 DNA binding domains (pink, red) attached to the DNA binding site. Image from Richard Wheeler, Wikipedia.

p53 is named such because it runs at 53 kDa on an SDS-PAGE gel. However, its actual mass is 43.7 kDa. Proline residues in the protein slow migration during electrophoresis, causing it to appear heavier than it actually is.

The p53 protein regulates many genes involved in cell cycle regulation and apoptosis, and therefore plays a critical role in maintaining genome stability. p53 accomplishes regulation of target genes by acting as a transcription factor. It binds to specific response elements in p53-regulated genes, controlling expression by either inducing or inhibiting transcription.

p53 is activated when the cell emits stress signals as a result of damage such as double-strand DNA breaks, protein unfolding, or oncogene activation. The severity of the damage as well as the point in the cell cycle at which p53 is activated will determine if the cell undergoes arrest and repair or apoptosis. The ability of p53 to induce apoptosis is critical to its function as a tumor suppressor. Inhibiting this process can lead to proliferation of damaged or toxic cells.



  1. Keri: p53: Introduction
  2. Keri: p53: Biological function
  3. Keri: p53: Biosynthesis
  4. Keri: p53: Gene sequence
  5. Keri: p53: Amino acid sequence and composition
  6. Keri: p53: Secondary and tertiary structure
  7. Keri: p53: Domains and structural motifs
  8. Keri: p53: Interactions with macromolecules and small molecules
  9. Keri: p53: Molecular biodiversity and evolution
  10. Keri: p53: Literature overview
  11. Keri: p53: Useful online resources
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