Platelet glycoprotein Ib alpha chain (GPIb a), also known as CD42ba, is a 145kD type I transmembrane protein that is a member of the leucine-rich repeat (LRR) family of ligand binding proteins.1-3 It is expressed by platelets as the ligand-binding subunit of the platelet GPIb-IX-V complex.4 Human GPIb a contains a 16 amino acid (aa) signal sequence, a 489 aa extracellular domain (ECD), a 21-aa transmembrane domain, and a 100 aa cytoplasmic region. The ECD contains 8 LRRs, with # 2, 3 and 4 having been demonstrated to regulate shear-dependent adhesion to von Willebrand factor (vWF).5, 6 The LRRs are followed by a thrombin-binding anionic region that includes three sulfated tyrosines, a sialomucin domain with N- and O-linked carbohydrates, and two cysteines near the membrane that allow dimerization with GP1bb.1-6 Four human isoforms with 1 to 4 repeats of aa 398-411 within the sialomucin domain of mature GPIb a are known to exist but have unknown significance.7 The ECD of human GPIb a shares 48-51% aa identity with mouse, rat, bovine and canine GPIb a. The metalloproteinase TACE/ADAM17 constitutively and inducibly cleaves GPIb a, between Gly 480 and Val 481. This releases a soluble form called glycocalicin that circulates at ~2 ug/mL.8, 9 GPIb a binding to ligands such as thrombin, kininogen, and coagulation factors XI and XII helps to initiate platelet activation and coordinate the coagulation cascade.1, 10-12 Binding of GPIb a to vWF or thrombospondin in the plasma or matrix, vWF or P-selectin on endothelial cells, or the integrin aMb2 (MAC-1) on myeloid cells, controls response to vascular injury.
A DNA sequence encoding the extracellular domain of human GPIb A (His17-Leu505; Swiss/UniProt Accession: P07359) was fused with a six-histidine tag at the C-terminus. The protein was expressed in NS0 cells line.
Calculated molecular mass of ~ 54.7kD. As a result of glycosylation, recombinant human GPIb a migrates as an ~ 95-120kD protein in SDS-PAGE under reducing conditions.
N Terminal Sequence Analysis:His 17
SDS-PAGE:~95-120kD, reducing conditions
Activity:Measured by its binding ability in a functional ELISA. Recombinant Human CD42b/GPIb alpha is immobilized at 0.5ug/ml (100ul/well), the concentration of Recombinant Human vWF-A2 that produces 50% optimal binding response is ~6-36ng/ml in the presence of ristocetin.
Storage and Stability:Lyophilized and reconstituted products may be stored at -20°C. Stable for 6 months after receipt at -20°C. Reconstitute with sterile PBS. Aliquot to avoid repeated freezing and thawing. Store at -20°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.
仕様
Size：50ug
Source Antigen：Recombinant, NS0 cells
Grade：Purified
Purity：≥90%, as determined by SDS-PAGE under reducing conditions and visualized by silver stain. Endotoxin: ≤1.0EU/ug (LAL)
Form：Supplied as a lyophilized powder from PBS, pH 7.4. Reconstitute with 500ul sterile PBS.
