Bert discovered the unique protein metallothionein, a low-molecular weight cysteine-rich protein. The protein binds zinc atoms very tightly and has been implicated in the homeostasis of zinc metabolism. It also binds many other metals tightly: the redox properties of copper, when bound to metallothionein, may be of significance in neurodegenerative diseases. Alcohol dehydrogenase, another zinc-containing enzyme, was of interest to Bert Vallee because of its role in alcohol metabolism and the general problem of alcohol addiction.