Key Physicochemical Determinants in the Antimicrobial Peptide RiLK1 Promote Amphipathic Structures.

Lucia Falcigno,Marco Balestrieri,Marta Gogliettino,Bruna Agrillo,Principia Dardano,Gabriella D’Auria,Rosarita Tatè,Luigi Nicolais,Gianna Palmieri

doi:10.3390/ijms221810011

Abstract

Antimicrobial peptides (AMPs) represent a skilled class of new antibiotics, due to their broad range of activity, rapid killing, and low bacterial resistance. Many efforts have been made to discover AMPs with improved performances, i.e., high antimicrobial activity, low cytotoxicity against human cells, stability against proteolytic degradation, and low costs of production. In the design of new AMPs, several physicochemical features, such as hydrophobicity, net positive charge, propensity to assume amphipathic conformation, and self-assembling properties, must be considered. Starting from the sequence of the dodecapeptide 1018-K6, we designed a new 10-aminoacid peptide, namely RiLK1, which is highly effective against both fungi and Gram-positive and -negative bacteria at low micromolar concentrations without causing human cell cytotoxicity. In order to find the structural reasons explaining the improved performance of RiLK1 versus 1018-K6, a comparative analysis of the two peptides was carried out with a combination of CD, NMR, and fluorescence spectroscopies, while their self-assembling properties were analyzed by optical and atomic force microscopies. Interestingly, the different spectroscopic and microscopic profiles exhibited by the two peptides, including the propensity of RiLK1 to adopt helix arrangements in contrast to 1018-K6, could explain the improved bactericidal, antifungal, and anti-biofilm activities shown by the new peptide against a panel of food pathogens.

Highlights

In recent decades, growing interest in antimicrobial peptides (AMPs) for their applications as bactericidal agents in different fields has been observed
Antimicrobial peptides (AMPs), known as host defense peptides (HDPs), are an important group of natural substances widely distributed in nature, offering a broad spectrum of activity against Gram-positive and Gram-negative bacteria, viruses, fungi, and parasites [2]
We reported the structural characterization of RiLK1 and 1018-K6 peptides in water and in SDS micellar solutions carried out by a combination of NMR, Circular dichroism (CD) and fluorescence spectroscopic techniques

Summary

Introduction

In recent decades, growing interest in antimicrobial peptides (AMPs) for their applications as bactericidal agents in different fields has been observed. The increased bacterial resistance due to the uncontrolled use of antibiotics has raised significant concerns in medicine, encouraging research into novel therapeutics [1,2,3] In this scenario, AMPs are considered a promising new class of antibiotics [4]. Due to the complexity of peptide–membrane interaction, the hydrophilicity/hydrophobicity properties must be finely balanced to optimize the activity and selectivity of AMPs avoiding cytotoxicity [20]. In this regard, the conformational features of AMPs play a key role [4,26]. The self-assembling properties of AMPs have received increasing attention in the rational design and engineering of smart AMPs [28,29,30,31,32]

Methods

Results

Conclusion