Conformational Changes of CaMKII: A Model of Activation

Abstract

The ubiquitously expressed calcium/calmodulin dependent protein kinase II (CaMKII) functions as a transducer of calcium (Ca2+) signaling by responding to the amplitude, duration, and frequency of Ca2+ transients. Autophosphorylation at Thr286 following binding of calcium-calmodulin (Ca2+/CaM) leads to a Ca2+-independent activity referred to as a conformational memory of prior activation. While CaM binding, autophosphorylation, and catalytic-regulatory domain autoinhibition have been linked to CaMKII function, the underlying structural and dynamic framework of activation and conformational memory is poorly understood. Here we utilize site-directed spin labeling and electron paramagnetic resonance (SDSL-EPR) to explore the conformational changes associated with CaMKII activation and conformational memory. The structure of the regulatory domain was investigated via spin label mobility under several conditions representing various intermediates of activation. Inter-domain movements were also examined through distance measurements between regulatory and catalytic domains. We found that CaMKII activation is associated with regulatory-catalytic domain disengagement, causing a disruption of autoinhibition and producing significant conformational changes which are propagated throughout the regulatory domain. Here we detail a mechanistic description of activation and are currently using EPR data to computationally model conformational changes associated with CaMKII activation.