Heavy-metal-binding protein. Involved in the maintenance of heavy metal homeostasis and/or in detoxification. A number of isoforms are produced. According to EST sequences. Expressed in petioles, hypocotyls, peduncles, vascular bundles and root meristems. Up-regulated by cadmium, Hg, Fe and Cu, but not by Mn or Co. Belongs to the HIPP family.