Biology:HA-tag

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. 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.

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. Labeling of endogenous proteins with HA-tag using CRISPR was recently accomplished in-vivo in differentiated neurons.

Sequence

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).

See also

• Protein tag
• SpyTag

Further reading

• "Purification of a RAS-responsive adenylyl cyclase complex from Saccharomyces cerevisiae by use of an epitope addition method". Molecular and Cellular Biology 8 (5): 2159–65. May 1988. doi:10.1128/MCB.8.5.2159. PMID 2455217.