Abstract
The Droserasins, aspartic proteases from the carnivorous plant Drosera capensis, contain a 100-residue plant-specific insert (PSI) that is post-translationally cleaved and independently acts as an antimicrobial peptide. PSIs are of interest not only for their inhibition of microbial growth, but also because they modify the size of lipid vesicles and strongly interact with biological membranes. PSIs may therefore be useful for modulating lipid systems in NMR studies of membrane proteins. Here we present the expression and biophysical characterization of the Droserasin 1 PSI (D1 PSI.) This peptide is monomeric in solution and maintains its primarily -helical secondary structure over a wide range of temperatures and pH values, even under conditions where its three disulfide bonds are reduced. Vesicle fusion assays indicate that the D1 PSI strongly interacts with bacterial and fungal lipids at pH 5 and lower, consistent with the physiological pH of D. capensis mucilage. It binds lipids with a variety of head groups, highlighting its versatility as a potential stabilizer for lipid nanodiscs. Solid-state NMR spectra collected at a field strength of 36 T, using a unique series-connected hybrid magnet, indicate that the peptide is folded and strongly bound to the membrane. Molecular dynamics simulations indicate that the peptide is stable as either a monomer or a dimer in a lipid bilayer. Both the monomer and the dimer allow the passage of water through the membrane, albeit at different rates.
Highlights
Plant carnivory has been considered as part of defense mechanisms involving the jasmonate pathway [1]
All sequences from the Drosera capensis genome [5] and the Dionaea muscipula transcriptome [22] that were previously annotated as coding for MEROPS A1 aspartic proteases using the MAKER-P (v2.31.8) pipeline [23] and a BLAST search against SwissProt and InterProScan [24] were examined for the presence of a plant-specific insert (PSI)
The genome of D. capensis contains at least six aspartic proteases with moderate sequence identity to mammalian pepsin (Droserasins 1–6) [5]
Summary
Plant carnivory has been considered as part of defense mechanisms involving the jasmonate pathway [1]. In species with flypaper traps, such as the Drosera, digestion generally occurs in an exposed environment over a prolonged period of time, without the benefit of a pitcher or closed trap. These plants catch prey in the sticky polysaccharide mucilage of their leaf tentacles, which wrap around the meal to increase contact with the digestive mucilage [2]. In the Droseracaea, the evolution of carnivory was accompanied by the loss of many genes common to other plants, and the concomitant expansion of genes related to carnivory [4] For these reasons, carnivorous plants are a potential source of novel and useful antimicrobial peptides as well as digestive enzymes. This plant is relatively cultivated and has been the target of genome sequencing [5] and enzyme discovery [6,7,8] efforts
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
