Mucin

Micrograph showing cells with prominent mucin-containing intracytoplasmic vacuoles. Pap stain.
Identifiers
Symbol	Mucin
Membranome	111

Mucins (/ˈmjuːsɪn/) are a family of high molecular weight, heavily glycosylated proteins (glycoconjugates) produced by epithelial tissues in most animals.^[1] Mucins' key characteristic is their ability to form gels; therefore they are a key component in most gel-like secretions, serving functions from lubrication to cell signalling to forming chemical barriers.^[1] They often take an inhibitory role.^[1] Some mucins are associated with controlling mineralization, including nacre formation in mollusks,^[2] calcification in echinoderms^[3] and bone formation in vertebrates.^[4] They bind to pathogens as part of the immune system. Overexpression of the mucin proteins, especially MUC1, is associated with many types of cancer.^[5][6]

Although some mucins are membrane-bound due to the presence of a hydrophobic membrane-spanning domain that favors retention in the plasma membrane, most mucins are secreted as principal components of mucus by mucous membranes or are secreted to become a component of saliva.