Related Experiment Video

Updated: Aug 15, 2026

Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors
10:33

Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors

Published on: October 26, 2015

Mechanism of Cdk2/Cyclin E inhibition by p27 and p27 phosphorylation

X Xu1, T Nakano, S Wick

  • 1Mitotix Inc., One Kendall Square, Cambridge, Massachusetts 02139, USA.

Biochemistry
|July 7, 1999
PubMed

Insights

The cyclin-dependent kinase 2 (Cdk2)/Cyclin E complex tightly inhibits cell cycle progression via p27, acting as a substrate rather than an enzyme when bound. This interaction is crucial for p27 degradation.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Cycle Regulation

Background:

  • Cyclin-dependent kinases (CDKs) regulate cell cycle progression.
  • p27 is a CDK inhibitor that plays a role in cell cycle control.
  • The interaction between Cdk2/Cyclin E and p27 is critical for cell cycle regulation.

Purpose of the Study:

  • To investigate the biochemical interactions between Cdk2/Cyclin E and its inhibitor p27.
  • To elucidate the mechanism of inhibition and substrate activity.
  • To clarify the role of p27 phosphorylation in its degradation.

Main Methods:

  • Purified recombinant p27 and CAK-phosphorylated Cdk2/Cyclin E were used.
  • Kinetic analyses (kcat/Km) were performed with histone H1 and pRb substrates.
  • IC50 values were determined at varying concentrations of Cdk2/Cyclin E, ATP, and histone H1.
  • Phosphorylation of p27 by Cdk2/Cyclin E was assessed.

Main Results:

  • Cdk2/Cyclin E exhibits 60-fold higher specificity for pRb than histone H1.
  • p27 acts as a tight-binding inhibitor of Cdk2/Cyclin E.
  • The Cdk2/Cyclin E/p27 complex is a kinetically inactive enzyme but serves as a substrate for Cdk2/Cyclin E.
  • p27 phosphorylation by Cdk2/Cyclin E occurs at high enzyme concentrations and targets the bound complex.

Conclusions:

  • The Cdk2/Cyclin E/p27 complex is a substrate, not an active enzyme.
  • Phosphorylation of p27 by Cdk2/Cyclin E targets the bound complex for potential degradation.
  • This clarifies the mechanism of p27 inhibition and its role in cell cycle control.

More Related Videos

Studying Cell Cycle-regulated Gene Expression by Two Complementary Cell Synchronization Protocols12:02

Studying Cell Cycle-regulated Gene Expression by Two Complementary Cell Synchronization Protocols

Published on: June 6, 2017

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay12:26

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay

Published on: May 3, 2018

Related Concept Videos

Positive Regulator Molecules01:45

Positive Regulator Molecules

To consistently produce healthy cells, the cell cycle—the process that generates daughter cells—must be precisely regulated.
Negative Regulator Molecules01:23

Negative Regulator Molecules

Positive regulators allow a cell to advance through cell cycle checkpoints. Negative regulators have an equally important role as they terminate a cell’s progression through the cell cycle—or pause it—until the cell meets specific criteria.
Positive Regulator Molecules02:39

Positive Regulator Molecules

Mitotic cell division results in daughter cells that exactly resemble the parent cell. However, errors in the DNA replication or distribution of genetic material may lead to genetic mutations that may be passed down to every new cell formed from the resulting abnormal cell. Propagation of such mutant cells is restricted through checkpoint mechanisms present at different stages of the cell cycle. These checkpoints involve regulator molecules that either promote or demote cell cycle events.
Inhibition of Cdk Activity02:34

Inhibition of Cdk Activity

The orderly progression of the cell cycle depends on the activation of Cdk protein by binding to its cyclin partner. However, the cell cycle must be restricted when undergoing abnormal changes. Most cancers correlate to the deregulated cell cycle, and since Cdks are a central component of the cell cycle, Cdk inhibitors are extensively studied to develop anticancer agents. For instance, cyclin D associates with several Cdks, such as Cdk 4/6, to form an active complex. The cyclin D-Cdk4/6 complex...
DNA Damage Can Stall the Cell Cycle02:36

DNA Damage Can Stall the Cell Cycle

In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...
Inhibition of CDK Activity02:34

Inhibition of CDK Activity

The orderly progression of the cell cycle depends on the activation of Cdk protein by binding to its cyclin partner. However, the cell cycle must be restricted when undergoing abnormal changes. Most cancers correlate to the deregulated cell cycle, and since Cdks are a central component of the cell cycle, Cdk inhibitors are extensively studied to develop anticancer agents. For instance, cyclin D associates with several Cdks, such as Cdk 4/6, to form an active complex. The cyclin D-Cdk4/6 complex...