Related Experiment Videos
Crystal structure of the CDK4/6 inhibitory protein p18INK4c provides insights into ankyrin-like repeat
R Venkataramani1, K Swaminathan, R Marmorstein
1Wistar Institute, Philadelphia, Pennsylvania, USA.
Abstract:
p18INK4c is a member of a family of INK4 proteins that function to arrest the G1 to S cell cycle transition by inhibiting the activity of the cyclin-dependent kinases 4 and 6. The X-ray crystal structure of the human p18INK4c protein to a resolution of 1.95 A reveals an elongated molecule comprised of five contiguous 32- or 33-residue ankyrin-like repeat units. Each ankyrin-like repeat contains a beta-strand helix-turn-helix extended strand beta-strand motif that associates with neighboring motifs through beta-sheet, and helical bundle interactions. Conserved ankyrin-like repeat residues function to facilitate the ankyrin repeat fold and the tertiary interactions between neighboring repeat units. A large percentage of residues that are conserved among INK4 proteins and that map to positions of tumor-derived p16INK4 mutations play important roles in protein stability. A subset of these residues suggest an INK4 binding surface for the cyclin-dependent kinases 4 and 6. This surface is centered around a region that shows structural features uncharacteristic of ankyrin-like repeat units.
Insights
The crystal structure of human p18INK4c reveals its role in cell cycle arrest. Key residues involved in protein stability and cyclin-dependent kinase binding were identified.
Area of Science:
- Molecular Biology
- Structural Biology
- Biochemistry
Background:
- p18INK4c is an INK4 protein family member.
- INK4 proteins regulate the cell cycle by inhibiting cyclin-dependent kinases 4 and 6 (CDK4/6).
- Cell cycle dysregulation is implicated in cancer development.
Purpose of the Study:
- To determine the X-ray crystal structure of human p18INK4c.
- To elucidate the structural basis for p18INK4c's function in cell cycle regulation.
- To identify potential binding sites for CDK4/6.
Main Methods:
- X-ray crystallography
- Protein structure determination to 1.95 A resolution.
- Structural analysis of protein-protein interactions.
Main Results:
- The human p18INK4c protein has an elongated structure composed of five ankyrin-like repeat units.
- Conserved residues within the ankyrin repeats are crucial for protein folding and stability.
- A potential CDK4/6 binding surface was identified, featuring unusual structural characteristics for ankyrin repeats.
Conclusions:
- The determined structure provides insights into the molecular mechanisms of p18INK4c.
- Structural features suggest a role in regulating cell cycle progression via CDK4/6 inhibition.
- Understanding p18INK4c structure may inform cancer therapeutic strategies targeting cell cycle control.