|Detection of Rat alpha 1-Microglobulin by Western Blot. Western blot shows rat plasma. PVDF membrane was probed with 0.5 µg/mL of Sheep Anti-Rat alpha 1-Microglobulin Antigen Affinity-purified Polyclonal Antibody (Catalog # AF7720) followed by HRP-conjugated Anti-Sheep IgG Secondary Antibody (Catalog # HAF016). A specific band was detected for alpha 1-Microglobulin at approximately 25 kDa (as indicated). This experiment was conducted under reducing conditions and using Immunoblot Buffer Group 1.|
Rat alpha 1-Microglobulin (alpha1-m/A1M; also protein HC) is a secreted, 25-26 kDa glycoprotein member of the lipocalin family, calycin superfamily of molecules. It is expressed by hepatocytes, keratinocytes, and endodermal derivatives in the embryo. A1M appears to act as a heme scavenger, protecting cells and collagen against oxidative damage. It also acts as an immunosuppressant, inhibiting polyclonal lymphocyte activation and dampening granulocyte migration in response to chemokines. A1M circulates either as a monomer, or bound to IgA, albumin or prothrombin. Rat A1M is generated through cleavage of a precursor molecule termed AMBP. This AMBP should not be confused with AMBP-1, a 120-140 kDa adrenomedullin-binding protein that is also known as Complement Factor H. The AMBP precursor contains a 19 aa signal sequence, an N-terminal 183 aa A1M protein (aa 20-202), and a C-terminal serine protease inhibitor termed bikunin (aa 205-349). A1M possesses one lipocalin domain (aa 41-186). Although cleavage of AMBP in the Golgi apparatus typically generates a 25 kDa A1M and 28 kDa bikunin molecule, the 55-65 kDa AMBP precursor can also be released intact. In human, A1M will undergo extracellular processing, generating an isoform that is missing the C-terminal four amino acids. There are four potential isoform variants. One utilizes an alternative start site at Met181, a second contains an Asn substitution for aa 112-228, a third possesses an 11 aa substitution for aa 1-141, and a fourth shows a 17 aa substitution for aa 201-349. Over aa 20-202, rat A1M shares 76% and 86% aa sequence identity with human and mouse A1M, respectively.