Recombinant Mouse FCRN Protein, CF

Recombinant Mouse FCRN Protein, CF Summary

Product Specifications

Product Datasheets

Carrier Free

CF stands for Carrier Free (CF). We typically add Bovine Serum Albumin (BSA) as a carrier protein to our recombinant proteins. Adding a carrier protein enhances protein stability, increases shelf-life, and allows the recombinant protein to be stored at a more dilute concentration. The carrier free version does not contain BSA.

In general, we advise purchasing the recombinant protein with BSA for use in cell or tissue culture, or as an ELISA standard. In contrast, the carrier free protein is recommended for applications, in which the presence of BSA could interfere.

Background: FCRN

The neonatal Fc receptor (FCRN) is an approximately 45 kDa transmembrane glycoprotein with structural homology to MHC class I proteins. It is widely expressed in endothelial and epithelial cells and plays an important role in IgG homeostasis (1). Mature mouse FCRN consists of a 276 amino acid (aa) extracellular domain (ECD) with two N-terminal alpha domains, one alpha 3/immunoglobulin-like domain, a 24 aa transmembrane segment, and a 44 aa cytoplasmic domain (2). Within the ECD, mouse FCRN shares 69% and 91% aa sequence identity with human and rat FCRN, respectively. Mouse FCRN binds with high affinity to IgG from mouse, human, rat, rabbit, guinea pig, bovine, and sheep, while human FCRN binds IgG with significantly lower affinity and is much more restricted in terms of species recognition (3). It does not bind the structurally related chicken IgY (4). FCRN additionally binds to albumin, and both it and IgG are bound at pH 5.0 but not at pH 8.0 (2, 5). FCRN associates noncovalently with beta 2-Microglobulin, and this interaction is important for the intracellular trafficking of FCRN (6 ‑ 9). FCRN cycles between the plasma membrane and acidified intracellular compartments of endothelial cells and epithelial cells (4, 7). It binds endocytosed IgG and albumin in the low pH vesicles and transports them to the plasma membrane for extracellular release at higher pH. This protects IgG and albumin from lysosomal degradation and helps maintain the circulating levels of both proteins (4, 5). This mechanism is involved in the bidirectional transport of IgG across epithelial and endothelial barriers including neonatal IgG absorption in the intestine and fetal uptake of maternal antibodies through the placenta (4, 7, 10, 11). In the kidney, FCRN recycles albumin to the serum but removes IgG from the glomular basement membrane and promotes its excretion into the urine (12, 13). FCRN is also expressed in neutrophils and myeloid antigen presenting cells (6, 14, 15). It can enhance IgG-mediated phagocytosis and antigen presentation by these cells, but it promotes the degradation of opsonizing IgG rather than returning it to the circulation (14, 15).

Related Research Areas

• Fc Receptors