Human influenza hemagglutinin (HA) is a glycoprotein required for the infectivity of the human virus and is expressed as a homotrimer on the surface of the viral capsid (1). As a major antigen of the influenza virus, HA constantly evolves to escape herd immunity via antigenic shift which can lead to pandemics (2). The HA tag (YPYDVPDYA-tag) itself has a molecular weight of 1.1 kDa and is a linear epitope derived from amino acids 98-106 of the HA protein. It is used extensively as a general epitope tag in expression vectors (2, 3). The HA tag is frequently added to the N- or C- terminus of a protein of interest to facilitate protein purification, detection, and labeling using anti-HA antibodies (3, 4). HA Tag is cleaved by caspase 3/7 resulting in total loss of immunoreactivity, making it unsuitable for the study of apoptosis (5).
1. Wilks, S., Graaf, M. D., Smith, D. J., & Burke, D. F. (2012). A review of influenza haemagglutinin receptor binding as it relates to pandemic properties. Vaccine, 30(29), 4369-4376. doi:10.1016/j.vaccine.2012.02.076
2. Wu, N. C., & Wilson, I. A. (2019). Influenza hemagglutinin structures and antibody recognition. Cold Spring Harbor Perspectives in Medicine, 10(8). doi:10.1101/cshperspect.a038778
3. Zhao, X., Li, G., & Liang, S. (2013). Several affinity tags commonly used in chromatographic purification. Journal of Analytical Methods in Chemistry, 2013, 1-8. doi:10.1155/2013/581093
4. Kimple, M. E., Brill, A. L., & Pasker, R. L. (2013). Overview of affinity tags for protein purification. Current Protocols in Protein Science, 73(1). doi:10.1002/0471140864.ps0909s73
5. Schembri, L., Dalibart, R., Tomasello, F., Legembre, P., Ichas, F., & Giorgi, F. D. (2007). The HA tag is cleaved and loses immunoreactivity during apoptosis. Nature Methods, 4(2), 107-108. doi:10.1038/nmeth0207-107
- HA epitope tag