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12CA5 Fv-clasp fragment (green, cyan) with its antigen peptide, YPYDVPDYA (magenta), which is used as HA tag. Image created with PyMOL from PDB: 5XCS​.

Human influenza hemagglutinin (HA) is a surface glycoprotein required for the infectivity of the human influenza virus. The HA-tag is derived from the HA-molecule corresponding to amino acids 98-106. HA-tag has been extensively used as a general epitope tag in expression vectors. [1] Many recombinant proteins have been engineered to express the HA-tag, which does not generally appear to interfere with the bioactivity or the biodistribution of the recombinant protein. This tag facilitates the detection, isolation and purification of the protein of interest.[2]

The HA-tag is not suitable for detection or purification of proteins from apoptotic cells since it is cleaved by Caspase-3 and / or Caspase-7 after its sequence DVPD, causing it to lose its immunoreactivity.[3] Labeling of endogenous proteins with HA-tag using CRISPR was recently accomplished in-vivo in differentiated neurons.[4]


The DNA sequences for the HA-tag include: 5'-TAC-CCA-TAC-GAT-GTT-CCA-GAT-TAC-GCT-3' or 5'-TAT-CCA-TAT-GAT-GTT-CCA-GAT-TAT-GCT-3'. The resulting amino acid sequence is YPYDVPDYA (Tyr-Pro-Tyr-Asp-Val-Pro-Asp-Tyr-Ala).[citation needed]

See also[edit]


  1. ^ Field J, Nikawa J, Broek D, MacDonald B, Rodgers L, Wilson IA, Lerner RA, Wigler M (1988). "Purification of a RAS-responsive adenylyl cyclase complex from Saccharomyces cerevisiae by use of an epitope addition method". Mol Cell Biol. 8 (5): 2159–65. doi:10.1128/mcb.8.5.2159-2165.1988. PMC 363397. PMID 2455217.
  2. ^ "Anti-HA Tag Antibody Updated 28/10/2021". Merck Millipore.
  3. ^ Schembri L, Dalibart R, Tomasello F, Legembre P, Ichas F, De Giorgi F (February 2007). "The HA tag is cleaved and loses immunoreactivity during apoptosis". Nature Methods. 4 (2): 107–8. doi:10.1038/nmeth0207-107. PMID 17264856. S2CID 32173039.
  4. ^ Mikuni T, Nishiyama J, Sun Y, Kamasawa N, Yasuda R (2016). "High Throughput, High Resolution Mapping of Protein Localization in Mammalian Brain by In Vivo Genome Editing". Cell. 165 (7): 1803–1817. doi:10.1016/j.cell.2016.04.044. PMC 4912470. PMID 27180908.

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