Homology between the Catalytic Subunits of Protein Phosphatases 1 and 2A Deduced from the cDNA
A wide variety of extracellular signals transmit information to the cell interior by activating transmembrane signalling systems that control the production of a relatively small number of chemical mediators or “second messengers”. These substances (cyclic AMP, cyclic GMP, diacylglycerol and calcium ions) each activate particular protein kinases allowing them to phosphorylate key regulatory proteins and so translate external signals into cellular responses1,2. However, the steady state level of phosphorylation of any protein depends on the activities of protein phosphatases, as well as protein kinases, raising two important questions. How many protein phosphatases are present in cells, and are they also controlled by “second messengers”?
KeywordsProtein Phosphatase Catalytic Subunit Glycogen Phosphorylase Cellular Regulation Rabbit Skeletal Muscle
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