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Owen Nadeau
Research Assistant Professor |
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Long-standing research interests are in protein structure and function, metalloenzymes and metal-binding proteins. My current focus centers on how subunit interactions affect the activation state of phosphorylase kinase (PhK), a hexadecameric oligomer comprising four copies of four distinct subunits, termed a, b, g and d, the last being endogenous calmodulin. In the holoenzyme, the catalytic g subunit is activated by neural (Ca2+), hormonal (cAMP and Ca2+) and metabolic (ADP) stimuli, which are integrated through allosteric sites on the regulatory a, b and d subunits. This activation of PhK by diverse physiological signals allows for tight control of glycogenolysis. Activation of PhK by Ca2+ in skeletal muscle directly links muscle contraction with energy production in the cascade activation of glycogen utilization.
I am employing a variety of approaches to determine mechanisms of how different signals alter subunit interactions in the holoenzyme, which in turn activate the catalytic g subunit. Protein cross-linking and synthetic peptides are used to identify interacting regions of adjacent subunits. Immunoelectron microscopy with monoclonal antibodies is used to localize regions of subunits within the tetrahedral structure of the enzyme. Immunochemistry and chemical modification are used to identify regions of the kinase that are influenced by allosteric effectors. Cryoelectron microscopy is used to determine changes in the overall structure of the kinase in response to the same effectors. The results from these different experimental approaches coalesce to define the relationships between specific subunit interactions and the control of activity for this important regulatory enzyme of mammalian energy production.
