Encrypted Antimicrobial Peptides from Plant Proteins

Abstract

Examples of bioactive peptides derived from internal sequences of proteins are known for decades. The great majority of these findings appear to be fortuitous rather than the result of a deliberate and methodological-based enterprise. In the present work, we describe the identification and the biological activities of novel antimicrobial peptides unveiled as internal fragments of various plant proteins founded on our hypothesis-driven search strategy. All putative encrypted antimicrobial peptides were selected based upon their physicochemical properties that were iteratively selected by an in-house computer program named Kamal. The selected peptides were chemically synthesized and evaluated for their interaction with model membranes. Sixteen of these peptides showed antimicrobial activity against human and/or plant pathogens, some with a wide spectrum of activity presenting similar or superior inhibition efficacy when compared to classical antimicrobial peptides (AMPs). These original and previously unforeseen molecules constitute a broader and undisputable set of evidences produced by our group that illustrate how the intragenic concept is a workable reality and should be carefully explored not only for microbicidal agents but also for many other biological functions.

Towards an experimental classification system for membrane active peptides

“…Twenty-one novel putative IAPs were filtered from the genomes of Theobroma cacao, Gossypium raimondii , Citrus sinensis, Arabidopsis thaliana and Zea mays , and selected for solid phase synthesis and testing, as reported in detail in the accompanying paper 7 . Many of these peptides were found to be as active as AMPs from conventional sources.…”

“…Indeed, such fragments derived from proteolysis, designated Intragenic Antimicrobial Peptides (IAPs), are currently being explored in biotechnological processes related to agriculture, human health and food conservation. Our methodology relies in two complementary steps: (1) the filtering of genomes/protein collections using a bioinformatic tool, “Kamal” 4 , 7 , which searches protein databases for fragments using a predefined set of physicochemical properties; and (2) an experimental classification tool to identify sets of IAPs which induce comparable disturbances in model phospholipid membranes. The latter was conceived to gain further insight in peptide-membrane interactions and to serve as a feedback to the selection process by refining the physicochemical parameters associated with a particular biological activity.…”

“…Peptides from one group, composed of known AMPs, perturbed the hydrocarbon core of model membranes, underwent conformational change to more α-helical segments upon membrane association, and presented high antimicrobial activity 4 . The physicochemical properties of this particular group, namely, average hydrophobicity, hydrophobic moment, net charge, among others, were fed back to the Kamal filtering algorithm 4 , allowing us to identify a further set of novel IAPs from plant genomes that serve as a basis for the current work 7 . Please refer to the literature for further details on the Kamal software and the physicochemical criteria used for the uncovering of IAPs 4 , 7 .…”

“…The physicochemical properties of this particular group, namely, average hydrophobicity, hydrophobic moment, net charge, among others, were fed back to the Kamal filtering algorithm 4 , allowing us to identify a further set of novel IAPs from plant genomes that serve as a basis for the current work 7 . Please refer to the literature for further details on the Kamal software and the physicochemical criteria used for the uncovering of IAPs 4 , 7 . The biological activities of these novel peptides are described in an accompanying report 7 , whilst here we focus on their physicochemical properties.…”

“…Please refer to the literature for further details on the Kamal software and the physicochemical criteria used for the uncovering of IAPs 4 , 7 . The biological activities of these novel peptides are described in an accompanying report 7 , whilst here we focus on their physicochemical properties. Future expansion of the currently presented methodology will assist the discovery of protein fragments with cell-penetrating and preamyloid activities and may provide a unified experimental framework for membrane active molecules.…”