Abstract
As the first crucial barrier in the midgut of insects, the peritrophic membrane (PM) plays an important role in preventing external invasion. PM proteins, as the major components of the PM, determine the structure and function of this membrane. A new PM protein, named LstiCBP, from the PM of Loxostege sticticalis larvae was identified using cDNA library screening. The full cDNA of LstiCBP is 2606 bp in length and contains a 2403 bp ORF that encodes an 808-amino acid preprotein with a 15-amino acid as signal peptide. The deduced protein sequence of the cDNA contains 8 cysteine-rich chitin-binding domains (CBDs). Recombinant LstiCBP was successfully expressed in BL21 cells using recombinant plasmid DNA and showed high chitin-binding activity. LstiCBP expression was detected in the midgut at both the transcriptional and translational levels; however, the biochemical and physiological functions of LstiCBP in L. sticticalis require further investigation.
Highlights
The peritrophic membrane, a structure in the gut of insects that is unique to invertebrates, is believed to be their initial protection from invasion by viruses, bacteria, protozoa, and helminthes, and it prevents damage to midgut cells by abrasive food particles [1,2,3]
Proteins are those that can be removed by washing with physiological buffers, Class 2 represents the peritrophic membrane (PM) proteins that are extractable by mild detergents, Class 3 PM proteins include those that are only extractable by strong denaturants, and Class 4 PM proteins are not extractable, even by strong denaturants
We identified a new PM chitin-binding protein, CBP, from L. sticticalis and found that cDNA clones for this protein were abundant in the non-normalized midgut cDNA expression library, which was in agreement with the previous observation that the majority of PM proteins are chitin-binding proteins
Summary
The peritrophic membrane, a structure in the gut of insects that is unique to invertebrates, is believed to be their initial protection from invasion by viruses, bacteria, protozoa, and helminthes, and it prevents damage to midgut cells by abrasive food particles [1,2,3]. Structural characterization of PM proteins has mainly focused on the following classes: peritrophins, invertebrate intestinal mucins, and proteins with chitin deacetylase domains [2,28]. Insect Intestinal Mucin (IIM) is a highly glycosylated, mucin-like protein that binds very strongly to the type 1PMs identified in Trichoplusiani larvae [10,29], and it contains peritrophin-A domains. (Lepidoptera: Pyralidae), is a polyphagous pest, which can feed on 35 families and 200 species plants and crops, such as corn, bean, potato, sugar beet, sunflower and so on. The new PM protein exhibits a strong chitin-binding activity, which allows the protein to perform its role in PM formation
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