Oligomeric structure of α-calmodulin-dependent protein kinase II

The subunit stoichiometry and symmetry of the neuronal α-calmodulin-dependent protein kinase II (αCaMKII) is investigated in this report to understand the structural basis of its regulation and mechanism at the molecular level. Two preparations are studied, αCaMKII obtained by overexpression in baculovirus-transfected insect cells and CaMKII isolated from rat forebrain. The structures, are studied by electron microscopy and image analysis. Single-particle analysis of individual molecular images reveals a molecule with a circular outline and pronounced 6-fold rotational symmetry of the central part. The central part has an outer radius of ∼6 nm and is composed of six lobes grouped around a hollow centre. The outer ring extends to ∼15 nm and consists of 12 apparent domains.