This limits the usefulness of Kaede as a fusion protein tag.

Functions as a protein tag with roles in nutrient sensing and oxidative stress response.

Enzymes may also be immobilized to a surface using non-covalent or covalent Protein tags.

This allows for affinity purification of proteins that are not well-behaved when fused to protein tags.

Protein tags are peptide sequences genetically grafted onto a recombinant protein.

For example, synthetic peptides can be used as probes to see where protein-peptide interactions occur- see the page on Protein tags.

The poly(His) tag is a widely-used protein tag; it binds to metal matrices.

These include gene knock-outs for functional genomics, or the 'knock-in' of protein tag insertions to track translocation events at physiological levels in live cells.

This requires a probe antibody which both recognizes the protein of interest and contains a detectable label, probes which are often available for known protein tags.

Cleavage of fusion protein so that the fusion partner and protein tag used in protein expression and purification may be removed.

A myc tag is a polypeptide protein tag derived from the c-myc gene product that can be added to a protein using recombinant DNA technology.

Recombinant T3SS proteins that carry a protein tag (a histidine tag, for instance) are produced by molecular cloning and then introduced (transformed) into the researched bacteria.

Many naturally occurring proteins do not have an affinity for metal ions, therefore recombinant DNA technology can be used to introduce such a protein tag into the relevant gene.

Protein tags find many other usages, such as specific enzymatic modification (such as biotin ligase tags) and chemical modification (FlAsH) tag.

The target protein is fused to the protein tag, but a protease cleavage site positioned in the polypeptide linker region between the protein and the tag allows the tag to be removed later.

In the overwhelming majority of cases, selected proteins are first "labeled" by the addition of several copies of a small protein tag called ubiquitin and are thus targeted for degradation in the proteasome (Figure 1).