Shotgun analysis on the peritrophic membrane of the silkworm Bombyx mori

Abstract

The insect midgut epithelium is generally lined with a unique chitin and protein structure, the peritrophic membrane (PM), which facilitates food digestion and protects the gut epithelium. We used gel electrophoresis and mass spectrometry to identify the extracted proteins from the silkworm PM to obtain an in-depth understanding of the biological function of the silkworm PM components. A total of 305 proteins, with molecular weights ranging from 8.02 kDa to 788.52 kDa and the isoelectric points ranging from 3.39 to 12.91, were successfully identified. We also found several major classes of PM proteins, i.e. PM chitin-binding protein, invertebrate intestinal mucin, and chitin deacetylase. The protein profile provides a basis for further study of the physiological events in the PM of Bombyx mori.

Fig. 1.. Protein Profiles of the silkworm PM in the 5th day of the fifth instar. (A): 1D SDS-PAGE pattern of PM proteins extracted from the B. mori. Each gel lane was cut into 7 bands (PM1 to PM7) followed by in-gel digestion used for shotgun analysis. The letters ‘M’ and ‘S’ represent protein marker and sample, respectively. (B): Distribution of isoelectric points (pI) and molecular weight (MW) for all of the proteins identified by the shotgun approach.

Fig. 2.. GO categories of the identified proteins in the silkworm PM. The identified proteins were classified into cellular component, molecular function, and biological process by WEGO, according to the GO terms.

Fig. 3.. Categories of commonly related pathways in PM according to KEGG pathway taxonomy. The pathways were methodically clustered into metabolism, genetic information processing, environmental information processing, cellular processes, and human diseases.