Recombinant CD81 protein (His tag)

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Recombinant Human CD81 Antigen (Fragment 113-201) is a high-purity, 89-amino acid fragment of the CD81 protein, also known as TAPA-1 or Tetraspanin-28. This fragment has been computationally selected for optimal stability and solubility, making it an ideal tool for structural studies, biochemical assays, and investigating the role of CD81 in immune signaling, viral entry, and cell adhesion mechanisms.

The full-length CD81 antigen is a 26 kDa cell surface protein and a key structural component of tetraspanin-enriched microdomains (TERMs), which serve as platforms for receptor clustering and signaling in immune cells. It plays critical roles in B cell activation by facilitating CD19-CR2/CD21 and B cell receptor complex assembly, lowering the threshold for antigen-triggered antibody production. In T cells, CD81 localizes CD247/CD3 zeta at immunological synapses, promoting costimulation and T helper type 2 polarization. Additionally, CD81 is involved in regulating cell-cell fusion processes—positively in sperm-egg fusion but negatively in macrophage and osteoclast fusion—and controls intracellular dNTP levels via SAMHD1 compartmentalization in T cells. CD81 also serves as a receptor for hepatitis C virus (HCV) entry in hepatocytes when associated with CLDN1, supports early HIV-1 replication via SAMHD1 degradation, and is essential for Plasmodium falciparum sporozoite infectivity in hepatocytes. As a multi-pass membrane protein, it localizes to the cell membrane, with CLDN1-CD81 complexes specifically found on the basolateral membrane in hepatocytes.