PROTEIN-KINASES - STRUCTURE AND FUNCTION

The solution of crystal structures from half a dozen protein kinases d uring the last four years in different laboratories has deepened our u nderstanding of the catalysis and regulation of this enzyme class, and given a vigorous impetus to the whole field. Due to the great degree of sequence conservation among protein kinases the informational yield with every new structure is high, as each is a representative of the enzyme family in general and most often of a subclass in particular, T his review will focus on the active site structure of cAMP-dependent p rotein kinase (cAPK) with special regard to two new crystal structures ; one of an active protein kinase CK1, which may represent an as yet unsolved step in the kinetic pathway, and the other of the insulin rec eptor kinase domain, the first structure of a tyrosine kinase.