The hemagglutinin (HA) tag is a 9-amino acid polypeptide derived from residues 90-106 of the human influenza virus HA molecule. It is a surface glycoprotein with a molecular weight of approximately 63 kDa related to human virus infection of cells. The HA tag is widely used as an epitope tag in expression vectors, facilitating the detection, isolation, and purification of proteins. Many recombinant proteins can be expressed with the HA tag because it does not interfere with the biological activity or distribution of the protein.
