The MT1A metallothionein binds 7 zinc(II) atoms, 3 at the N-terminal beta domain and 4 at the C-terminal alpha domain (Sunderland et al. 2012). Binding is non-cooperative (Sunderland et al. 2012) and occurs via thiolate bonds between zinc and cysteine residues of the protein. MT1A binds 5 atoms of zinc before clustering of the zinc occurs (Summers et al. 2013). The 2 remaining zinc atoms bind MT1A with significantly less affinity (Summers et al. 2013).