• Purity

  >95%, by SDS-PAGE under reducing conditions and visualized by silver stain

• Endotoxin Level

  <0.10 EU per 1 μg of the protein by the LAL method.  

• Activity

  Measured by the ability of the immobilized protein to support adhesion of J45.01 human acute lymphoblastic leukemia T lymphocytes. Liang, T.W.     et al. (2002) J. Immunol.     168:1618.

  When Recombinant Human JAM-B Fc Chimera is immobilized on goat anti-human IgG Fc Chimera antibody coated wells, J45.01 cells (100 µL/well at 10⁶ cells/mL) adhesion is induced in a dose dependent manner after a 2 hour incubation at 37 °C. The ED₅₀ for this effect is 10-60 ng/mL.

• Source

  Mouse myeloma cell line, NS0-derived

  Human JAM-B (Phe29 - Asn236) Accession # P57087	IEGRMD	Human IgG1 (Pro100 - Lys330)
  N-terminus		C-terminus

• Accession #

• N-terminal Sequence    
  Analysis

  Phe29

• Structure / Form

  Disulfide-linked homodimer

• Predicted Molecular Mass

  50 kDa (monomer)

• SDS-PAGE

  64-70 kDa, reducing conditions

Background: JAM-B/VE-JAM

The family of juctional adhesion molecules (JAM), comprising at least three members, are type I transmembrane receptors belonging to the immunoglobulin (Ig) superfamily (1, 2). These proteins are localized in the tight junctions between endothelial cells or epithelial cells. Some family members are also found on blood leukocytes and platelets. JAM-B, alternatively named vascular endothelial JAM (VE-JAM), is expressed prominently on high endothelial venules of lymphoid organs where it is localized to the intercellular boundaries of high endothelial cells. It is also expressed on the endothelium of a variety of non-lymphoid organs, especially the heart and placenta (3, 5). Human JAM-B cDNA predicts a 298 amino acid residue (aa) precursor protein with a putative 28 aa signal peptide, a 209 aa extracellular region containing two Ig domains, a 23 aa transmembrane domain and a 38 aa cytoplasmic domain containing a PDZ-binding motif and a PKC phosphorylation site. Human JAM-B shares approximately 79% aa sequence homology with its mouse homologue. It also shares approximately 35% aa sequence homology with human JAM-A or JAM-C. JAM-B exhibits homotypic interactions, as well as heterotypic interactions with JAM-C, but not JAM-A (4, 5, 7). It is also a ligand for the integrin alpha ₄ beta ₁. However, the JAM-B/ alpha ₄ beta ₁ interaction is facilitated only after prior adhesion of JAM-B to JAM-C (6). Through its heterotypic interactions with JAM-C, JAM-B is an adhesive ligand for T, NK, and dendritic cells, and may play a role in regulating leukocyte transmigration (5).

The nomenclature used for the JAM family proteins is confusing. VE-JAM has been referred in the literature variously as JAM-B or JAM-3. Until further clarification, R&D Systems has adopted the nomenclature where both mouse and human VE-JAM are referred to as JAM-B.

• References:

1. Chavakis, T. et al. (2003) Thromb. Haemost. 89:13.

2. Aurand-Lions, M. et al. (2001) Blood 98:3699.

3. Palmeri, A. et al. (2000) J. Biol. Chem. 275:19139.

4. Cunnigham, S. et al. (2000) J. Biol. Chem. 275:34750.

5. Liang, T. et al. (2002) J. Immunol. 168:1618.

6. Cunningham, A. et al. (2002) J Biol. Chem. 277:27589.

7. Arrate, M. et al. (2001) J. Biol. Chem. 276:45826.

• Long Name:

  Junctional Adhesion Molecule B

• Entrez Gene IDs:

  58494 (Human); 67374 (Mouse)

• Alternate Names:

  C21orf43; CD322 antigen; CD322; JAM2; JAMB; JAM-B; JAM-BJAM-IT/VE-JAM; junctional adhesion molecule 2JAM-2; junctional adhesion molecule B; PRO245; Vascular endothelial junction-associated molecule; VE-JAM; VE-JAMVEJAMCD322