Characterization of an intestinal mucin from the peritrophic matrix of the diamondback moth, Plutella xylostella

The peritrophic matrix (PM) of Plutella xylostelia larvae was found to contain twelve integral and eighteen loosely associated proteins. An antiserum against Mamestra configurata integral PM proteins cross-reacted with several P xylostelia PM proteins and was used to isolate a partial cDNA encoding an insect intestinal mucin (PxIIM). PxIIM was expressed primarily in the larval midgut. The deduced protein sequence of the partial cDNA contained three potentially glycosylated, mucin-like domains and six cysteine-rich chitin-binding domains (CBDs). An additional chitin-binding domain was proposed to reside at the amino terminus of the protein based on comparison with other IIM. The organization of mucin domains and CBDs exhibited features, including an internal triplet of regularly spaced CBDs and a carboxyl terminal CBD with two additional conserved cysteine residues, that were found to be common to other lepidopteran IIMs.