What is the Avi-Tag? The Avi‑Tag is a short peptide tag of 15 amino acids. Its defined sequence is Gly-Leu-Asn-Asp-Ile-Phe-Glu-Ala-Gln-Lys-Ile-Glu-Trp-His-Glu. When this sequence is genetically fused to either the N-terminus or C-terminus of a target protein, it functions as a specific recognition site for the biotin ligase enzyme (commonly B