Metal-binding protein

Example metal binding proteins

Saccharomyces cerevisiae MT metallothionein bound to copper ions. Cysteines in yellow, copper in brown. (PDB: 1AQS​)

Cyanobacterial SmtA metallothionein bound to zinc ions. Cysteines in yellow, zinc in purple. (PDB: 1JJD​)

Metal-binding proteins are proteins or protein domains that chelate a metal ion.^[1]

Binding of metal ions via chelation is usually achieved via histidines or cysteines. In some cases this is a necessary part of their folding and maintenance of a tertiary structure. Alternatively, a metal-binding protein may maintain its structure without the metal (apo form) and bind it as a ligand (e.g. as part of metal homeostasis). In other cases a coordinated metal cofactor is used in the active site of an enzyme to assist catalysis.