Structural Insights into the Regulation of Ca2+/Calmodulin-Dependent Protein Kinase II (CaMKII).

Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a highly conserved serine/threonine kinase that is ubiquitously expressed throughout the human body. Specialized isoforms of CaMKII play key roles in neuronal and cardiac signaling. The distinctive holoenzyme architecture of CaMKII, with 12-14 kinase domains attached by flexible linkers to a central hub, poses formidable challenges for structural characterization. Nevertheless, progress in determining the structural mechanisms underlying CaMKII functions has come from studying the kinase domain and the hub separately, as well as from a recent electron microscopic investigation of the intact holoenzyme. In this review, we discuss our current understanding of the structure of CaMKII. We also discuss the intriguing finding that the CaMKII holoenzyme can undergo activation-triggered subunit exchange, a process that has implications for the potentiation and perpetuation of CaMKII activity.