Recombinant Human
Apolipoprotein M/ApoM Catalog Number: 4550-AM
DESCRIPTION Source E. coliderived Cys23Asn188, with an Nterminal Met and 6His tag Accession # NP_061974
Nterminal Sequence Met & Thr62 Analysis Predicted Molecular 19.5 kDa Mass
SPECIFICATIONS SDSPAGE 1921 kDa, reducing conditions
Activity Measured by its ability to bind alltransretinoic acid. The concentration of alltransretinoic acid required to quench 50% of Trp fluorescence in Recombinant Human Apolipoprotein M/ApoM is approximately 1050 μM.
Endotoxin Level <0.10 EU per 1 μg of the protein by the LAL method.
Purity >95%, by SDSPAGE under reducing conditions and visualized by silver stain. Formulation Lyophilized from a 0.2 μm filtered solution in PBS. See Certificate of Analysis for details.
PREPARATION AND STORAGE Reconstitution Reconstitute at 500 μg/mL in PBS.
Shipping The product is shipped at ambient temperature. Upon receipt, store it immediately at the temperature recommended below. Stability & Storage Use a manual defrost freezer and avoid repeated freezethaw cycles. l 12 months from date of receipt, 20 to 70 °C as supplied. l 1 month, 2 to 8 °C under sterile conditions after reconstitution. l 3 months, 20 to 70 °C under sterile conditions after reconstitution.
BACKGROUND Apolipoprotein M (ApoM) is an approximately 25 kDa variably glycosylated protein that adopts a betabarrel structure characteristic of lipocalin family proteins. It functions as a component of lipoprotein particles which play essential roles in fatty acid and cholesterol transport and metabolism (1, 2). Human ApoM shares 83% amino acid sequence identity with mouse and rat ApoM (3). Alternative splicing generates a short isoform that lacks the Nterminal 72 amino acids. ApoM is produced primarily by hepatocytes but also by renal tubule epithelial cells (4). The signal peptide is not cleaved and is required for ApoM association with lipoprotein particles as well as Megalin mediated reabsorption by the kidney (5, 6). ApoM is cleared from the circulation by the ubiquitously expressed LDL R (7, 8). The majority of circulating ApoM is associated with HDL, while a smaller fraction is associated with LDL (3, 9, 10). It promotes the intracellular formation of large prebeta (discoidal) HDL particles which inhibit the development of atherosclerotic plaques by facilitating the efflux of cellular cholesterol and preventing phospholipid oxidation (7, 9, 1113). The lipocalin structure of ApoM enables it to function as a carrier protein for small hydrophobic molecules including retinol (Vitamin A), alltransretinoic acid, 9cisretinoic acid, and sphingosine1phosphate (S1P) (14, 15). ApoM delivers S1P to S1P1 receptors and contributes to the maintenance of vascular endothelial integrity (15).
References: 1. Christoffersen, C. and L.B. Nielsen (2013) Curr. Opin. Lipidol. May 6 Epub. PMID 23652568. 2. Arkensteijn, B.W. et al. (2013) Int. J. Mol. Sci. 14:4419. 3. Xu, N. and B. Dahlback (1999) J. Biol. Chem. 274:31286. 4. Zhang X.Y. et al. (2003) Acta Histochem. 105:67. 5. Christoffersen, C. et al. (2008) J. Biol. Chem. 283:18765. 6. Faber, K. et al. (2006) Mol. Endocrinol. 20:212. 7. Christoffersen, C. et al. (2010) Circ. Res. 106:1624. 8. Christoffersen, C. et al. (2012) J. Lipid Res. 53:2198. 9. Christoffersen, C. et al. (2008) J. Biol. Chem. 283:1839. 10. Christoffersen, C. et al. (2006) J. Lipid Res. 47:1833. 11. Mulya, A. et al. (2010) J. Lipid Res. 51:514. 12. Wolfrum, C. et al. (2005) Nat. Med. 11:418. 13. Elsoe, S. et al. (2012) Atherosclerosis 221:91. 14. Ahnstrom, J. et al. (2007) J. Lipid Res. 48:1754. 15. Christoffersen, C. et al. (2011) Proc. Natl. Acad. Sci. USA 108:9613.
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