Proteins metal binding

Before we conclude the functions of the elements and the proteome, there is a second general feature of eukaryote cells, much of which evolved from that of the prokaryotes - the types of metal-binding protein. The general supposition is that the number of folds are limited and certainly the number of metal-binding sites for any one metal ion is closely limited (see Section 4.15). We find that there are some general rules for protein-binding centres of metal ions and their geometry, mentioned only in brief in Chapters 5 and 6. 

Metal chelate affinity chromatography finds most prominent application in the affinity purification of recombinant proteins to which a histidine tag has been attached (described later). As protein binding occurs via the histidine residues, this technique is no more inherently useful for the purification of metalloproteins than for the purification of non-metalloproteins (a common misconception, given its name). 

Cysteine can bind to either one or two metal ions, and is frequently found as a ligand to iron (in Fe-S clusters—see later) and to Cu+ (for example in the copper chaperones, which transfer copper to specific copper-binding proteins). Histidine can bind metal ions in two... 

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