Protein purification tags

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Overview of tags added to protein to facilitate their purification

We are missing info on TAP-tag and evalution/comparison of the techniques. Jasu 18:09, 3 March 2007 (EST)

amino acid tags

A stretch of amino acids is added to the protein and enables the recovery of the labelled protein by its unique affinity. Usually its easiest to add the tag to either end of the protein to ensure its accessibility and not to disturb the protein folding.

His tag / IMAC

6+ histidine (His) residues
recovered by affinity to nickel or cobalt column

- more on the His tag in the Wikipedia

FLAG tag

N-DYKDDDDK-C and others
recovered with specific antibody

- - more on FLAG-tag in the Wikipedia
- protocol for purification of His-tagged protein, Kafatos lab
- protocol for purification of His-tagged protein, Wittrup lab

HA tag

fusion with an epitope derived from the Influenza protein haemagglutinin (HA): e.g. N-YPYDVP-C
recovery with an HA antibody

- Wikipedia entry on haemagglutinin
- Clontech: HA tag
- Roche HA tag vector (PDF)

MYC tag

fusion with an epitope derived from the human proto-oncoprotein MYC: e.g. N-ILKKATAYIL-C, N-EQKLISEEDL-C
recovery with an MYC antibody

- Wikipedia entry on Myc oncogene
- MACS-MYC vector from Miltenyi Biotec (PDF)
- combined MYC/FLAG tag vector from Stratagene

protein tags

Rather than adding only a few amino acids a whole protein is fused to the protein to be purified or detected. The affinity of the attached protein enables the recovery of the artificial fusion protein. As for the peptides, the protein tag is added to either end of the target protein.

GST tag

fusion with the small glutathione-S-transferase (GST; 26 kDa)
recovery by affinity to substrate glutathione bound to a column, e.g. glutathione sepharose

- GST cloning system of GE Healthcare
- Wikipedia entry on GST

chemical tags

biotin - streptavidin

linking amino acids, often lysines, to cofactor and vitamin biotin
purification by tight binding to streptavidin-agarose or -beads

- Wikipedia entry biotin
- Wikipedia entry streptavidin and avidin
- Biotin purification reagents from IBA