Human HPRG Antibody

Human histidine‑rich glycoprotein (HPRG) is a multidomain, monomeric, secreted, 67‑75 kDa member of the cystatin superfamily of molecules (1, 2). Its name derives from the fact that 26% of its amino acids (aa) are histidine and proline. In human, it is synthesized as a 525 aa precursor that contains an 18 aa signal sequence and a 507 aa mature region (3). Five distinct domains are recognized in the mature molecule. There are two N‑terminal cystatin‑like modules (aa 19‑254) and one His‑Pro‑rich region (aa 350‑497) that is flanked by two Pro‑rich segments (aa 276‑321 and 498‑525) (3, 4). The His‑Pro‑rich region contains 10 tandem repeats with an HHPHG motif, and the N‑ and C‑termini are linked by a disulfide bond (3, 5, 6). Human HPRG is only 60% aa identical to mouse HPRG. There are multiple ligands for HPRG. These include small molecular weight molecules (metal ions; heme), hemostatic molecules (heparan sulfate; TSP; plasminogen), and immune system components (T cells; macrophages) (1, 5). About 50% of plasma plasminogen circulates bound to HPRG. Upon immobilization to cell surface tropomyosin in a Zn⁺⁺‑dependent manner, it is converted to plasmin by tPA (7‑9). HPRG also shows antiangiogenic activity on endothelial cells (10).