|Protein Name||Mucin 1|
|Ref Sequence Id||NP_776540.1|
|Amino Acid Lenth||580|
|Protein Existence Status||Reviewed: Experimental evidence at protein level|
|Presence in other biological fluids/tissue/cells||mammary, salivary, lung, pancreas, kidney and stomach|
|Protein Function||integral membrane component; glycosylated molecule of MUCl on the surface of epithelia presents a physical barrier protecting the cell; anti-invasion characteristics;roles as a growth inhibitor; at digestion;protecting membrane proteins from protease action;being a large, extended membrane protein, it may shield other nearby residents.|
|Biochemical Properties||rich in serine, threonine,proline, alanine and glycine; rigid, extended molecule due to random coil promoting properties of prolines and the further rigidity conferred by glycosylation; beneficial characteristic of MUCl is its relative durability, especially its resistance to proteases|
|Significance in milk||MUCl may be a factor regulating size of MFGs, membrane secretion, and fat content of milk; sialic acid of mucins on MFGs prevent their clumping and clogging the ducts through which they must pass|
|PTMs||glycoprotein; 50% carbohydrate, 30% of which was sialic acid; polymorphic and carbohydrate portion is of variable nature; serine and threonine hydroxyls provide sites for glycosylation; human milk MUC1 has high galactose, modest level of sialic acid, and lack of detectable mannose; bovine MUC1 has less galactose, significant mannose and much higher sialic acid; galactose and N-acetylglucosamine are the dominant sugars in the human mucin; O-linked oligosaccharides are comprised of a core unit attached to MUCl via N-acetylgalactosamine, a backbone, and a terminal region; The core and backbone may be branched and the ends may be terminated by sialic acid, galactose, fucose or N-acetylgalactosamine; Sulfation may also occur at the periphery;|
|Significance of PTMs||The oligosaccharides carry substantial sialic acid at their termini and this accounts for two putative functions of this mucin, i.e., to keep ducts and lumens open by creating a strong negative charge on the surface of epithelial cells which would repel opposite sides of a vessel, and to bind certain pathogenic microorganisms; sialic acid content in terminal positions on oligosaccharides of the mucin confers a negative charge to the extracellular surface,that might prevent wall to wall adherence in lumens and ducts thus preventing their closure and preserving the integrity of secretory systems|
|Bibliography||1. Patton, S., Huston, G. E., Jenness, R., & Vaucher, Y. (1989). Differences between individuals in high-molecular weight glycoproteins from mammary epithelia of several species. BBA - Biomembranes, 980(3), 333–338. https://doi.org/10.1016/0005-2736(89)90321-0. |
2. Schroten, H., Hanisch, F. G., Plogmann, R., Hacker, J., Uhlenbruck, G., Nobis-Bosch, R., & Wahn, V. (1992). Inhibition of adhesion of S-fimbriated Escherichia coli to buccal epithelial cells by human milk fat globule membrane components: a novel aspect of the protective function of mucins in the nonimmunoglobulin fraction. Infection and Immunity, 60(7), 2893–2899. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/1377184.
3. Mather, I. H., & Keenan, T. W. (1975). Studies on the structure of milk fat globule membrane. The Journal of Membrane Biology, 21(1–2), 65–85. https://doi.org/10.1007/bf01941062.