Antimicrobial Peptides: Structure and Mechanism of Biological Activity 2.0

Dear Colleagues,

Since the early 1960s, the resistance of microbes against antibiotics has been recognized as a potential global health issue. This issue is now critical due to the reemergence of several infectious diseases of microbial origin and prevalence of multidrug-resistant microbes. Antimicrobial peptides (AMPs) have offered a good potential for novel drugs against drug-resistant microbial organisms, and extensive research has been dedicated to the discovery, characterization, de novo design, and assessment of the antimicrobial activity of these peptides since the late 1980s. So far, more than 3000 AMPs have been characterized and documented. These peptides have diverse natural origins and are found in unicellular organisms (bacteria, archaea, protists, and fungi), plants, and animals. Close to 75% of AMPs are found in animals, ~11% in plants, and about the same number in bacteria. Based on the sequences of these naturally found peptides, new chemically modified synthetic peptides have been designed to enhance or modify the biological activity of the original peptides. AMPs are also diverse in their biological activities and can be multifunctional. In addition to their antimicrobial activity, AMPs can have other biological functions, such as antioxidant, anticancer, antimalarial, chemotactic (modulation of immune systems), and wound healing. The diversity of AMPs expands to their physicochemical properties, structure, and mechanism of biological activity, which are the foci of this Special Issue. Most, but not all, AMPs are positively charged, and negatively and neutrally charged peptides can also be found. AMPs have different structures (α-helix, β-sheet, turn, or nonspecific interconvertible dynamic structures), overall hydrophobicity and amphipathicity, and can be linear, cyclic, or a combination of both. Many AMPs interact with the lipid membranes of the microbial/nonmicrobial cells and destroy these cells by disrupting the osmotic balance across the membrane. Some AMPs can pass across cell membranes and interact with intracellular targets such as organelle membranes, receptor proteins, or DNA.

In the late 1980s and during the 1990s, several models were proposed for the mechanism of interaction of AMPs with model cell membranes, which generally include self-association of peptides and/or peptide–lipid association from specific well-defined pores or to induce nonspecific leakage. The mechanisms of translocation of AMPs through cell membranes and their successive interaction with intracellular molecules are less investigated. Understanding and visualizing the structural dynamics (subtle and fast conformational changes prior to and after interaction with cell membranes) and the entirety of the complex biophysical nature of the mechanism of the biological activity of AMPs are essential steps toward the discovery and design of new antimicrobial peptide drugs. 

Prof. Dr. Masoud Jelokhani-Niaraki
Guest Editor

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