Recombinant Human Transcobalamin II Protein, CF

Recombinant Human Transcobalamin II 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: Transcobalamin II

Transcobalamin II (TCII) is an approximately 44 kDa protein that serves as a circulating carrier for cobalt‑containing Vitamin B₁₂ (also known as Cobalamin, or Cbl). Vitamin B₁₂ plays an important role as a coenzyme during amino acid and nucleotide metabolism. Chronic deficiency of Vitamin B₁₂ intake, absorption, or transport leads to serious health risks including megaloblastic anemia and neurologic symptoms. Prior to its interaction with TCII, dietary Vitamin B₁₂ is bound by salivary Transcobalamin I (Haptocorrin) which shields it from the acidic environment of the stomach. Vitamin B₁₂ is subsequently transferred to Transcobalamin III (also known by its traditional name Intrinsic Factor, or IF) following the proteolytic degradation of Transcobalamin I in the small intestine. Transcobalamin III- Vitamin B₁₂ complexes are internalized into intestinal epithelial cells (IEC) by Cubam, which is a receptor complex containing the proteins Cubilin and Amnionless (1). IF is degraded within the IEC, while free Vitamin B₁₂ is transcytosed and actively pumped across the basolateral membrane by the efflux transporter MRP1 (2, 3). Here, Vitamin B₁₂ is picked up by TCII, which is secreted by vascular endothelial cells into the interstitial space between IEC (4). TCII binds to free Vitamin B₁₂ with high affinity and is critical for the passage of Vitamin B₁₂ into the blood stream (5, 6). Circulating TCII- Vitamin B₁₂ complexes are bound and internalized by the widely expressed TCII Receptor, also known as CD320 and 8D6A (7). A soluble form of CD320 circulates in the serum (8). TCII is then degraded intracellularly, and Vitamin B₁₂ can function as a cofactor for methionine synthase and methylmalonyl-CoA mutase (1). In the kidney, TCII- Vitamin B₁₂ complexes are filtered and reabsorbed through interactions with Megalin on proximal tubule epithelial cells (9). Megalin also directly interacts with CD320 in these cells (10). CD320 is additionally expressed on placental membranes for Vitamin B₁₂ delivery to the developing fetus (11). Mature human TCII shares 74% amino acid (aa) sequence identity with mouse and rat TCII (12). Alternative splicing of human TCII generates a short isoform with a 27 aa internal deletion.