mucin-5AC; mucin-5 subtype AC, tracheobronchial; tracheobronchial mucin; TBM; major airway glycoprotein; gastric mucin; Lewis B blood group antigen; LeB (MUC5AC, MUC5)

Function

• gel-forming glycoprotein of gastric & respiratory tract epithelia that protects the mucosa from infection & chemical damage by binding to inhaled microrganisms & particules that are subsequently removed by the mucocilary system
• may be required for proper folding of these regions & for export from the endoplasmic reticulum during biosynthesis
• proteolytic cleavage in the C-terminal is initiated early in the secretory pathway & does not involve a serine protease
• extent of cleavage is increased in the acidic parts of the secretory pathway
• cleavage generates a reactive group which could link MUC5AC to a primary amide
• interacts with H pylori in the gastric epithelium, Barrett's esophagus as well as in gastric metaplasia of the duodenum

Structure

• multimeric
• S-, O- & N-glycosylated
• O-glycosylated on the Thr-/Ser-rich tandem repeats
• S-mannosylation in the Cys-rich subdomains
• the Cys in the Cys-rich subdomain repeats are not involved in disulfide bonding
• contains 1 CTCK (C-terminal cystine knot-like) domain
• contains 2 VWFC domains
• contains 4 VWFD domains

Compartment

secreted

Expression

• highly expressed in surface mucosal cells of respiratory tract & stomach epithelia
• overexpressed in a number of carcinomas
• expressed in Barrett's esophagus epithelium & in the proximal duodenum

More general terms

• mucin
• secreted protein

Database

• OMIM: https://mirror.omim.org/entry/158373
• UniProt: http://www.uniprot.org/uniprot/P98088.html