Table 1.
Mucins in the gastrointestinal tract.
| Mucin* (and type) | Protein domains‡ |
Number of amino acids |
Number of mucin domains (and estimated length of mucin domains§) |
Cell type expression |
Function | Reference |
|---|---|---|---|---|---|---|
| MUC1 (transmembrane) | 1 SEA | ~1,250 | 1 (~200 nm) | Epithelial cells | Signalling, protection |
30, 118–124 |
| MUC2 (gel-forming) | 4 VWD, 2 CysD, 1 CK |
~5,200 | 2 (~550 nm) | Goblet cells Paneth cells |
Protection, lubrication, entrapment |
13, 50, 125, 126 |
| MUC3II (transmembrane) | 1 SEA | >2,550 | 1 (>350 nm) | Enterocytes | Apical surface protection |
127 – 129 |
| MUC4 (transmembrane) | 1 NIDO, 1 AMOP, 1 VWD |
~5,300 | 1 (~800 nm) | Epithelial cells Goblet cells |
Signalling, protection |
130-133 |
| MUC5AC (gel-forming) | 4 VWD, 11 CysD, 1 CK |
>5,050 | 11 (>350 nm) | Mucous cells | Protection, lubrication, entrapment |
57, 134–138 |
| MUC5B (gel-forming) | 4 VWD, 7 CysD, 1 CK |
~5,700 | 7 (~550 nm) | Mucous cells Goblet cells |
Protection, lubrication, entrapment |
139 – 141 |
| MUC6 (gel-forming) | 1 VWD, 1 CK |
~2,400 | 1 (~250 nm) | Mucous cells | Protection, lubrication, entrapment |
142 – 144 |
| MUC7 (gel-forming) | None | 377 | 1 (~230 nm) | Mucous cells | Protection | 41, 145 |
| MUC12 (transmembrane) | 1 SEA | ~5,500 | 1 (~1000 nm) | Enterocytes | Apical surface protection |
26 |
| MUC13 (transmembrane) | 1 SEA | 512 | 1 (~30 nm) | Enterocytes | Apical surface protection? |
27, 146 |
| MUC16 (transmembrane) | 33 SEA | ~22,000 | 1 (~2400 nm) | Epithelial cells | Apical surface protection |
147, 148 |
| MUC17 (transmembrane) | 1 SEA | ~4,500 | 1 (~800 nm) | Enterocytes | Apical surface protection |
149 |
*
Human mucin nomenclature is used. A curated database of mucin gene and protein sequences can be found at www.medkem.gu.se/mucinbiology/databases.
‡
In addition to mucin domains (glycosylated PTS domains).
§
Total length of all mucin domains. Length = 0.2nm/amino acid.
II
Two MUC3 genes A and B have been proposed to exist.150 Abbreviations: AMOP, adhesion associated domain in MUC4 and other proteins; CysD, Cystein D domain interrupting mucin domains; CK, cysteine knot; GF, Gelforming; SEA, sea urchin-enterokinase-agrin domain, and agrin domain; NIDO, nidogen-like domain; S, Secreted (not polymeric); VWD, von Willebrand.