Anti‐microbial peptides: from invertebrates to vertebrates

Abstract

Gene-encoded anti-microbial peptides (AMPs) are widespread in nature, as they are synthesized by microorganisms as well as by multicellular organisms from both the vegetal and the animal kingdoms. These naturally occurring AMPs form a first line of host defense against pathogens and are involved in innate immunity. Depending on their tissue distribution, AMPs ensure either a systemic or a local protection of the organism against environmental pathogens. They are classified into three major groups: (i) peptides with an alpha-helical conformation (insect cecropins, magainins, etc.), (ii) cyclic and open-ended cyclic peptides with pairs of cysteine residues (defensins, protegrin, etc.), and (iii) peptides with an over-representation of some amino acids (proline rich, histidine rich, etc.). Most AMPs display hydrophobic and cationic properties, have a molecular mass below 25-30 kDa, and adopt an amphipathic structure (alpha-helix, beta-hairpin-like beta-sheet, beta-sheet, or alpha-helix/beta-sheet mixed structures) that is believed to be essential to their anti-microbial action. Interestingly, in recent years, a series of novel AMPs have been discovered as processed forms of large proteins. Despite the extreme diversity in their primary and secondary structures, all natural AMPs have the in vitro particularity to affect a large number of microorganisms (bacteria, fungi, yeast, virus, etc.) with identical or complementary activity spectra. This review focuses on AMPs forming alpha-helices, beta-hairpin-like beta-sheets, beta-sheets, or alpha-helix/beta-sheet mixed structures from invertebrate and vertebrate origins. These molecules show some promise for therapeutic use.

Membrane interactions of designed cationic antimicrobial peptides: The two thresholds

“…To distinguish among the isomeric peptides, we specify Leu positions along the sequence by subscript numbers at the end of each peptide designation. CAPs with inter-molecular disulfide bonds form a major class of innate immune system agents, 3,4 and peptide cyclization is a known tool for metabolic stability improvement through global conformational constraint on otherwise more flexible structure(s). 30,31 This tactic has been applied successfully on magainin II 32 and mellitin 33 sequences, also demonstrating that linearity of the peptides is not essential for the disruption of the target phospholipid membrane.…”

“…1 Antimicrobial peptides successfully serve as the key innate immunity agents for a wide range of species ranging from plants and insects to mammals and limit colonization and infection by bacteria, fungi, parasites and enveloped viruses and demonstrate synergy with conventional antibiotics. Some antimicrobial peptides are also effective against tumor cells [2][3][4][5] and have been proposed to play a role in the regulation of inflammatory responses. 6 Antimicrobial peptides share a limited number of characteristics, including relatively short length (a few tens of residues), net positive charge, 7 and solubility in water or saline.…”

A defensin from clam Venerupis philippinarum: Molecular characterization, localization, antibacterial activity, and mechanism of action

“…AMPs represent potential substitutes for antibiotics due to their broad specificity against bacteria or fungi, and their anti-viral, anti-tumoral, anti-inflammatory, wound-healing, and immunomodulatory activities (Diamond et al, 2009;Otero-González et al, 2010). Despite being evolutionary ancient, AMPs exhibit great diversity in terms of structural features, biological properties and functions, and also in their tissue distribution and expression profiles (Bachere et al, 2004;Bulet et al, 2004).…”

cDNA sequence and expression analysis of an antimicrobial peptide, theromacin, in the triangle-shell pearl mussel Hyriopsis cumingii

“…Antimicrobial peptides (AMPs) (also called as host-defense peptides) are evolutionarily conserved components of the innate immune system that play an important role in phagocytosis and local and systemic killing of microbes; these compounds are found in both vertebrates and invertebrates (Bachère et al, 2004;Bulet et al, 2004). Unlike the majority of conventional antibiotics, AMPs may also possess the ability to enhance immunity by functioning as immunomodulators.…”