HA-tag

An HA-tag is composed of a peptide derived from the HA-molecule corresponding to amino acids 98-106, which can be recognized and selectively bound by commercially available antibodies.

This makes HA a powerful tool in molecular biology, commonly included in expression vectors and in the production of recombinant proteins.

[2] As a result HA-tags are often used to identify protein-protein interactions or to detect protein expression, using Co-Immunoprecipitation or Western blot respectively.

[3][4] 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.

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

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 ​.