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High affinity calmodulin target sequence in the signalling molecule PI 3-kinase
R Fischer1, J Julsgart, M W Berchtold
1Institute of Molecular Cell Biology, University of Copenhagen, Denmark.
FEBS Letters
|April 16, 1998
Summary
Phosphatidylinositol 3-kinase (PI 3-kinase) binds calmodulin (CaM) with high affinity. This calcium-dependent interaction reveals a novel regulatory mechanism linking calcium and phospholipid signaling pathways.
Area of Science:
- Biochemistry
- Cell Signaling
- Molecular Biology
Background:
- Phosphatidylinositol 3-kinase (PI 3-kinase) is a crucial lipid kinase involved in signaling pathways downstream of G protein-coupled receptors and receptor tyrosine kinases.
- Understanding PI 3-kinase regulation is vital for deciphering cellular responses to various stimuli.
Purpose of the Study:
- To investigate the interaction between PI 3-kinase and calmodulin (CaM).
- To identify a potential novel regulatory mechanism for PI 3-kinase activity.
Main Methods:
- Gel shift analysis to detect complex formation.
- Fluorescence spectrophotometry and dansylated CaM titration to quantify binding affinity.
- Sequence comparison across PI 3-kinase isoforms.
Main Results:
- A high-affinity binding site for CaM was identified on PI 3-kinase.
- The interaction between the p110gamma isoform peptide and CaM is calcium-dependent.
- An affinity constant of 5 nM was determined for the CaM-peptide complex.
- The CaM-binding sequence is conserved among different PI 3-kinase isoforms.
Conclusions:
- PI 3-kinase directly interacts with CaM in a calcium-dependent manner.
- This interaction represents a novel mechanism for regulating PI 3-kinase activity.
- A direct link between calcium and phospholipid signaling pathways is established.