Autophosphorylation of multifunctional Ca2+/calmod-ulin-dependent protein kinase converts it from a Ca2+-dependent to a Ca2+-independent or autonomous kinase, a process that may underlie some long-term enhancement of transient Ca2+ signals. We demonstrate that the neuronal α subunit clone expressed in COS-7 cells (α-CaM kinase) is sufficient to encode the regulatory phenomena characteristic of the multisubunit kinase isolated from brain. Activity of α-CaM kinase is highly dependent on Ca2+/calmodulin. It is converted by autophosphorylation to an enzyme capable of Ca2+-independent (autonomous) substrate phosphorylation and autophosphorylation. Using site-directed mutagenesis, we separately eliminate five putative auto-phosphorylation sites within the regulatory domain and directly examine their individual roles. Ca2+/calmodulin-dependent kinase activity is fully retained by each mutant, but Thr286 is unique among the sites in being indispensable for generation of an autonomous kinase.
ASJC Scopus subject areas