Fig 2. CaMKII holoenzyme state transitions.

(A) Our model of CaMKII has twelve individual subunits arranged in two radially symmetric, directly apposed rings. Subunits may spontaneously undock/extend from the central hub or dock/retract (if inactive). Whether docked or undocked, subunits may spontaneously open/activate. (B) If two neighboring subunits are active, one may auto-phosphorylate the other at Thr-286. If auto-phosphorylated (pThr-286), a subunit may remain active even upon un-binding of CaM. A pThr-286 subunit un-bound to CaM may additionally phosphorylate at Thr-306, blocking subsequent re-binding of Ca²⁺/CaM. A pThr-286 subunit may also bind and become de-phosphorylated by PP (purple).