| CD99 antigen-like 2 (CD99-L2) is a 45kD type I transmembrane glycoprotein in the CD99 family of molecules (1-3). Mouse CD99-L2 cDNA encodes a 214 amino acid (aa) precursor with a 23 aa predicted signal sequence, a 116 aa extracellular domain (ECD), a 21 aa transmembrane segment, and a 54 aa cytoplasmic region (4). The ECD contains no N-linked glycosylation sites, but O-linked glycosylation is likely (1, 2). A long isoform with a 23 aa insert after aa 43 within the ECD is expressed in human, and probably in mouse (2, 5). Both long and short isoforms may have minor variants missing portions of the N-terminus of the mature protein (6). The ECD of mouse CD99-L2 short isoform shares 85%, 72% and 66% aa identity with rat, human, and bovine CD99-L2, respectively (3, 5). The mouse CD99 and CD99-L2 ECDs share only 31% aa identity, but both contain three conserved acidic motifs and are thought to originate from the same ancestral gene (1, 2). The nearly ubiquitous expression of CD99-L2 is similar to that of CD99. Mouse CD99-L2 shows highest in situ hybridization signals in neurons, cortical thymocytes, ganglia, ovarian granulosa cells, testis, and kidney, and detectable protein levels in lung, thymocytes, mouse leukocytes and vascular endothelial cells (2, 7). CD99-L2 expression on endothelial cells is reported to mediate cell aggregation and neutrophil or monocyte extravasation to inflamed tissue in vivo, while CD99 mediates lymphocyte extravasation as well (3, 7). Source: A DNA sequence encoding the extracellular domain of human CD99-L2 (Val 20-Ala 188, Accession NP_113650) was fused to the Fc region of human IgG1 via a peptide linker. The chimeric protein was expressed in Chinese Hamster Ovary cells. Molecular Mass: The recombinant human CD99-L2/Fc is a disulfide linked homodimeric protein. Based on N-terminal amino acid sequencing, the recombinant human CD99-L2/Fc starts at Val 20. Each monomer has a calculated molecular mass of approximately 44.5kD. The recombinant human CD99-L2 migrates as an approximately 65-75kD protein in SDS-PAGE under reducing conditions. Activity: Measured by its ability to bind biotinylated rmCD99-L2 in a functional ELISA type binding assay. Storage and Stability: Lyophilized and reconstituted products are stable for 6 months after receipt at -20C. Reconstitute with sterile PBS. Aliquot to avoid repeated freezing and thawing. Store at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer. |
