High affinity calmodulin target sequence in the signalling molecule PI 3-kinase
Related Experiment Video
Updated: Oct 30, 2026

Pull-down of Calmodulin-binding Proteins
Published on: January 23, 2012
R Fischer1, J Julsgart, M W Berchtold
1Institute of Molecular Cell Biology, University of Copenhagen, Denmark.
Abstract:
In this study we report that phosphatidylinositol 3-kinase (PI 3-kinase), a lipid kinase which participates in downstream signalling events of heterotrimeric G protein-coupled receptors and receptor tyrosine kinases, contains a high affinity binding site for calmodulin (CaM). The putative CaM-binding peptide derived from the p110gamma isoform interacts with CaM in a calcium-dependent way. Using gel shift analysis and fluorescence spectrophotometry we discovered that the peptide forms a high affinity complex with CaM. Titration experiments using dansylated CaM gave an affinity constant of 5 nM. Furthermore, a sequence comparison among different PI 3-kinase isoforms revealed that the sequence which can bind CaM is highly conserved within different PI 3-kinase isoforms. These results indicate a novel mechanism for regulating PI 3-kinase and provide a new direct link between Ca2+ and phospholipid signalling pathways.
Related Concept Videos
Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
PI3K/mTOR/AKT Signaling Pathway
IP3/DAG Signaling Pathway
Amplifying Signals via Second Messengers
Amplifying Signals via Enzymatic Cascade
The JAK-STAT Signaling Pathway
