Molecular characterization of a peritrophic membrane protein from the silkworm, Bombyx mori.

The peritrophic membrane lines the gut of most insects at one or more stages of their life cycles. It facilitates the digestive processes in the guts and protects from invasion by pathogens or food particles. In the current study, a novel PM protein, designated as BmMtch, was identified from the silkworm, Bombyx mori. The open reading frame of BmMtch is 888 bp in length, encoding 295 amino acid residues consisting of two domains (Mito_carr domains) and three transmembrane regions. They are localized on the 11th chromosome as single copy with one exon only. Quantitative real time PCR analysis (qRT-PCR) revealed that BmMtch was mainly expressed in larval fat bodies, Malpighian tubules, testis and ovaries, and could be detected through all stages of the life cycle of silkworm. Immuno-fluorescence analysis indicated that BmMtch was localized within the goblet cell of larval midgut. Western blotting analysis showed that BmMtch were detected in total proteins of PM and larval midgut. The characteristics of BmMtch indicated that BmMtch represents a novel member of insect PM proteins, without chitin-binding domains.