Fig. 3.

Regulation of mammalian NM-2 enzymatic activity and assembly state. RLC kinases promote the conformational change of the inhibited (10S) to the extended NM-2 conformation (6S). The inhibited conformation is assembly-incompetent, the extended conformer assembly-competent. MLCP activity shifts the equilibrium towards the inhibited conformation. The transition to the extended conformation triggers the activation of NM-2 ATPase activity and promotes the assembly of NM-2 homodimers into bipolar filaments. NMHC phosphorylation or binding of the calcium-binding protein Mts1 promotes NM-2 filament disassembly. NMHC phosphorylation impairs Mts1 binding. Mechanisms underlying NMHC dephosphorylation are unknown