Searching for assembled peptides from Ostrinia furnacalis cuticle proteome

Abstract

Insect cuticle is a complex protein self-assembly system. However, the assembly mechanism is poorly understood. At present, most of the research on insect cuticular proteins focus on resilin, which but little attention has been paid to a vast majority of cuticular proteins. With the help of transcriptome analysis, hundreds of insect cuticular proteins have been discovered, yet little is known about the properties of these proteins. This thesis presents an important method to screen functional sequences of insect cuticle protein sequences by analyzing the repetitive sequences in insect cuticle proteome. Nine unreported repetitive peptide sequences were obtained based on the threshold filtering. I discovered that three special sequences within these peptides exhibited liquid - liquid phase separation (LLPS) behavior in mixed organic-water solvents. More interestingly, these liquid peptide droplets gradually transformed into hollow vesicles. This transformation was attributed to the slow formation of the β-sheet structure which was revealed on ThT fluorescent labelling and Fourier Transform Infrared Spectroscopy. The size of the peptide vesicles could be controlled at the nanometer scale by the addition of cross-linking agents. I also demonstrate that such insect cuticle peptide vesicles can be excellent vehicles for drug delivery applications. Model proteins and anti-cancer drugs were successfully delivered to Hela cells using these insect cuticle peptides vesicles.