Related Experiment Videos
High molecular weight calmodulin-binding protein is phosphorylated by calmodulin-dependent protein kinase VI from
1Department of Pathology, College of Medicine, University of Saskatchewan, Saskatoon, Canada.
Insights
Researchers purified a novel calmodulin-dependent protein kinase (CaMK VI) from bovine heart. This kinase specifically phosphorylates a high molecular weight calmodulin-binding protein (HMW CaMBP) in a calcium/calmodulin-dependent manner.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Signaling
Background:
- Calmodulin (CaM) is a crucial calcium-binding protein involved in regulating numerous cellular processes.
- CaM-dependent protein kinases (CaMKs) play vital roles in signal transduction pathways.
- Characterization of novel CaMKs is essential for understanding complex cellular signaling networks.
Purpose of the Study:
- To purify and characterize a novel CaM-dependent protein kinase from bovine heart cytosol.
- To identify and investigate the substrate specificity of the novel kinase.
- To determine if the novel kinase is related to previously identified CaMKs.
Main Methods:
- Purification of high molecular weight calmodulin-binding protein (HMW CaMBP) from bovine heart cytosol.
- Gel filtration chromatography to initially identify the CaM-dependent protein kinase.
- Sequential chromatography including DEAE-Sepharose, CaM-Sepharose, phosphocellulose, Sepharose 6B, and Mono S columns for protein kinase purification.
- Stoichiometric phosphorylation assays to determine substrate specificity and reaction kinetics.
Main Results:
- A novel CaM-dependent protein kinase with an apparent molecular mass of 36,000 daltons was purified to homogeneity.
- The purified kinase stoichiometrically phosphorylated HMW CaMBP in a Ca2+/CaM-dependent manner.
- Phosphorylation incorporated 1 mol of phosphate per mol of HMW CaMBP.
- The kinase exhibited distinct substrate specificity, differentiating it from known CaMKs I-V.
Conclusions:
- A novel CaM-dependent protein kinase, designated CaM-dependent protein kinase VI (CaMK VI), has been identified and purified from bovine heart.
- CaMK VI specifically phosphorylates HMW CaMBP, suggesting a unique role in cardiac cellular signaling.
- The distinct substrate specificity indicates CaMK VI represents a new class of CaM-dependent protein kinases.
Abstract:
A high molecular weight calmodulin-binding protein (HMW CaMBP) from bovine heart cytosolic fraction was purified to apparent homogeneity. A novel CaM-dependent protein kinase was originally discovered when the total CaM-binding protein fraction from cardiac muscle was loaded on a gel filtration column. The CaM-dependent protein kinase was shown by gel filtration chromatography to have an apparent molecular mass of 36,000 daltons. The CaM-dependent protein kinase has been highly purified by sequential chromatography on DEAE-Sepharose Cl 6B (to remove calmodulin), CaM-Sepharose 4B, phosphocellulose, Sepharose 6B gel filtration and Mono S column chromatographies. The highly purified protein kinase stoichiometrically phosphorylated the HMW CaMBP in a Ca2+/CaM-dependent manner. The phosphorylation resulted in the maximal incorporation of 1 mol of phosphate/mol of the HMW CaMBP. The distinct substrate specificity of this protein kinase indicates that it is not related to the known protein kinases (I, II, III, IV and V) that have been already characterized, therefore we would like to designate this novel kinase as a CaM-dependent protein kinase VI.