ABSTRACT
The reader is referred to numerous reviews on specific protein kinases (PKs) and groups of protein kinases which have appeared. It is not clear whether homologous feedback systems are a common feature of protein kinases, but it will be interesting to see if the systems described for cAK and PK-C are examples of more general phenomena. The two proteins also share structural similarities, particularly in their respective camp binding domains. Certain structural features associated with particular functions have been conserved among all the members of the PK family. Weber et al. found substantial sequence homology and suggested that the two enzymes may have higher order structural similarities. The two enzymes, originally thought to be a single enzyme, are now known to exhibit multiple forms and vary in their physical and kinetic characteristics. The noted homology between the two classes of PTKs also extends to a number of the serine/threonine protein kinases.
