The metallothionein binds 7 atoms of cadmium(II) in 2 clusters, 4 atoms at the C-terminal alpha domain and 3 atoms at the N-terminal beta domain (Palumaa et al. 2002, Palumaa et al. 2005, Wu et al. 2014). MT3 binds cadmium with a lower affinity than MT2A does (Palumaa et al. 2005). MT3 can bind more than 7 cadmium atoms, however the MT3:7Cd2+ complex is most prevalent (Palumaa et al. 2002, Palumaa et al. 2005). Exposure of MT3:7Cd2+ to nitric oxide causes release of cadmium (Wang et al. 2008).