Functions as an intestinal M-cell transcytotic receptor specific of type-I-piliated bacteria that participates in the mucosal immune response toward these bacteria. At the apical membrane of M-cells it binds fimH, a protein of the bacteria type I pilus tip. Internalizes bound bacteria, like E.coli and S.typhimurium, from the lumen of the intestine and delivers them, through M-cells, to the underlying organized lymphoid follicles where they are captured by antigen-presenting dendritic cells to elicit a mucosal immune response. Interacts with SYCN. Secreted, after cleavage, in the pancreatic juice. Expressed in pancreas (at protein level) (PubMed:8666297, PubMed:10760606). Specifically expressed by M (microfold) cells which are atypical epithelial cells of the intestine (at protein level) (PubMed:19907495). N-glycosylated. It is uncertain whether Met-1 or Met-8 is the initiator.