Assays of protein kinases using exogenous substrates

In studies of the regulation of specific biochemical events by reversible phosphorylation, assaying the protein kinases themselves can often lead to significant progress in understanding the mechanistic details of a system under study. This unit describes assays for a variety of protein kinases that require different conditions to detect and measure their activities: cyclic nucleotide-dependent kinases, protein kinase C and isoforms, casein kinases, Ca(2+)/calmodulin-dependent kinases, and tyrosine kinase. A protocol for in-gel assays for specific kinase activity is also provided. The unit is not meant to be a catalog of individual protein kinase assays; however, the general principles of these assays should apply to most if not all known protein kinases.