Metallothioneins have a high content of cysteine residues that bind various heavy metals (Probable). Functions as metal chelator of copper (Cu) and zinc (Zn) (PubMed:18287486). Plays a role in Cu homeostasis, specifically in the remobilization of Cu from senescing leaves. The mobilization of Cu from internal sources is important for seed development (PubMed:24635746). A number of isoforms are produced. According to EST sequences. Expressed in leaf mesophyll cells, root tips, and at low levels in anthers. Belongs to the metallothionein superfamily. Type 15 family.