DDR1, also known as CAK, CD167a, RTK6, and TrkE, is a 120-140kD type I transmembrane glycoprotein that belongs to the discoidin-like domain containing subfamily of receptor tyrosine kinases (1, 2). Mature human DDR2 consists of a 398 amino acid (aa) extracellular domain (ECD) that includes the discoidin-like domain, a 27 aa transmembrane segment, and a 470 aa cytoplasmic region with a tyrosine kinase domain (3). Within the ECD, human DDR1 shares 53% aa sequence identity with human DDR2 and 93% with mouse and rat DDR1. DDR1 is expressed on epithelial tissues, activated monocytes and neutrophils, and in several cancers (2, 4). Compared to isoform DDR1b, DDR1a lacks 37 aa’s that include a Shc-interacting NPxY motif in the cytoplasmic juxtamembrane region (5). Two additional kinase deficient splice forms are expressed in colon cancer (6). The discoidin-like domain mediates binding to collagens I-V (1, 7, 8). DDR1 selectively recognizes the triple helical structure of collagen (7, 8). It is expressed on the cell surface as a dimer which can include different isoforms (5, 9). DDR1 oligomerization enhances collagen binding and also modulates collagen fibrillogenesis (10, 11). The transmembrane segment contains a leucine zipper and GxxxG motif, but neither is exclusively required for dimerization (9). Collagen binding induces prolonged autophosphorylation, including the NPxY motif (7, 8). Collagen binding also results in the proteolytic cleavage of a tyrosine phosphorylated 60kD C-terminal fragment (CTF), and a 60kD ECD fragment (12, 13). TIMP3 and TAPI-1 inhibit shedding of the ECD fragment but not the CTF (12). Overexpression of DDR1a promotes MMP-2 activation and results in an increased invasiveness of a glioblastoma cell line; DDR1b does not (14).
The recombinant human DDR1/Fc is a disulfide-linked homodimeric protein. Based on N-terminal amino acid sequencing, the recombinant protein starts at Asp 21. Each monomer has a calculated molecular mass of approximately 70.5kD. As a result of glycosylation, recombinant human DDR1 migrates as an approximately 90-95kD protein on a SDS-PAGE under reducing conditions.
Hybridoma:NSO myeloma cells with spleen cells from Balb/c mice. A DNA sequence encoding the extracellular domain of human DDR1 was fused with the Fc region of human IgG 1 via a linker peptide. The chimeric protein was expressed in a mouse myeloma cell line, NS0.
Activity:Measured by its ability to bind Collagen I in a functional ELISA [Leitinger, B. (2003) J. Biol. Chem. 278:16761]. Immobilized Collagen I at 10ug/ml (100ul/well) can bind rhDDR1 with an apparent KD <10nM.
Storage and Stability:Lyophilized powder may be stored at -20°C to -70°C and is stable for 12 months at the given storage temperatures. Reconstitute at 0.1mg/ml with sterile PBS. For long term storage, a carrier protein (e.g. 0.1% HSA or BSA) should be added to the vial. Aliquot and store at -20°C to 70°C. Reconstituted product is stable for 3 months at -20°C to -70°C . 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.
Purity：≥85% (SDS-PAGE and visualized by silver stain). Endotoxin: <1EU/ug (LAL)
Form：Supplied as a lyophilized powder in PBS. Reconstitute with 500ul sterile PBS. For long term storage a carrier protein (e.g. 0.1% HSA or BSA) should be added to the vial.
