• Purity

  >95%, by SDS-PAGE under reducing conditions and visualized by silver stain

• Endotoxin Level

  <0.10 EU per 1 μg of the protein by the LAL method.  

• Activity

  Measured by its binding ability in a functional ELISA. Immobilized rhCubulin at 1 µg/mL can bind rhAmnionless with an apparent    
  K    _D < 100 nM.

• Source

  Mouse myeloma cell line, NS0-derived Val20-Ala358, with a C-terminal 10-His tag

• Accession #

• N-terminal Sequence    
  Analysis

  Val20

• Predicted Molecular Mass

  37.2 kDa

• SDS-PAGE

  41-42 kDa, reducing conditions

Background: Amnionless

Amnionless (AMN) is an approximately 48 kDa type I transmembrane protein that is required for surface expression of the extracellular membrane-associated protein Cubilin (1 - 5). The two form a complex termed CUBAM (4, 5). The 453 amino acid (aa) human AMN precursor contains a 19 aa signal sequence, a 338 aa extracellular domain (ECD), a 21 aa transmembrane domain, and a 75 aa cytoplasmic domain. The ECD contains two potential N-glycosylation sites and a cysteine-rich vWFC domain. Two cytoplasmic consensus FxNPxP/F sequences for clathrin-coated pit targeting mediate endocytosis of compounds bound by Cubulin (3, 5). The ECD of human AMN shares 67%, 66%, 76% and 78% aa identity with mouse, rat, canine and bovine AMN, respectively. AMN is present during gastrulation in the visceral endoderm and required for primitive streak formation during embryonic development in mouse (6). Transcription from an alternate start site in humans results in an isoform starting at M55 that may also function in development (7). AMN is highly expressed on polarized epithelia in the apical brush border membranes of small intestine and kidney proximal convoluted tubules (3 - 5, 7). Intestinal CUBAM is required for absorption of cobalamin (vitamin B12) when complexed with intrinsic factor (IF), and mutations of AMN or Cubilin cause Imersund-Grasbeck syndrome, also called megaloblastic anemia-1 (4, 5, 7). In the kidney, the CUBAM complex is thought to be important for reabsorption of proteins from filtrate, notably albumin and the molecules it carries (3, 8). Cubilin or CUBAM can be tightly associated with megalin, another endocytic receptor that contributes to stable expression of Cubilin, and to uptake of vitamin and lipoprotein complexes in the kidney and placenta (1, 9).

• References:

1. Kozyraki, R. and F. Gofflot (2007) Curr. Pharm. Des. 13:3038.

2. Coudroy, G. et al. (2005) J. Am. Soc. Nephrol. 16:2330.

3. Strope, S. et al. (2004) Development 131:4787.

4. He, Q. et al. (2005) Blood 106:1447.

5. Fyfe, J.C. et al. (2004) Blood 103:1573.

6. Kalantry, S. et al. (2001) Nat. Genet. 27:412.

7. Tanner, S.M. et al. (2003) Nat. Genet. 33:426.

8. Birn, H. (2006) Am. J. Physiol. Renal Physiol. 291:F22.

9. Ahuja, R. et al. (2008) Biochem. J. 410:301.

• Entrez Gene IDs:

  81693 (Human); 93835 (Mouse)

• Alternate Names:

  AMN; amnionless homolog (mouse); Amnionless; PRO1028; protein amnionless; UNQ513/PRO1028; visceral endoderm-specific type 1 transmembrane protein