Identification and characterization of novel cecropins from the Oxysternon conspicillatum neotropic dung beetle

Abstract

Dung beetles are exposed to a complex microbiological ecosystem during their life cycle. Characterization of novel host-defense peptides (HDP) is essential to understanding the host innate immune response in insects. It constitutes a promising alternative to look for new therapeutic agents against pathogenic microbes. We identified four new HDP, Oxysterlins 1, 2, 3, and 4 from the transcriptome of the Oxysternon conspicillatum dung beetle. These HDP display a highly conserved signal peptide and a mature peptide, characterized by an overall positive charge (cationic) (pI: 10.23–11.49), a hydrophobic ratio (ΦH: 35–41), and amphipathicity. Oxysterlins 1, 2, and 3 have a linear α-helix structure, whilst Oxysterlin 4 has a mixture of both α-helix and β-sheet structures without disulfide bonds through bioinformatics prediction and circular dichroism. Oxysterlins are part of the cecropin family group in an exclusive clade related to beetle cecropins. They have predominant antimicrobial activity against Gram-negative bacteria, including multidrug resistant strains (3.12–50 μg/mL) measured by plate microdilution. Their kinetics, in a time-killing curve showed concentration-dependent bactericidal activity. Furthermore, these HDP have low toxicity against human erythrocytes (62.5–500 μg/mL) and Vero cells (250–500 μg/mL). This article describes new HDP of the cecropin family from the Oxysternon conspicillatum dung beetle, with antimicrobial activity against multidrug resistant bacteria and low toxicity.

Toward insights on determining factors for high activity in antimicrobial peptides via machine learning

“…The observation made in this study is consistent with previous experimental results of Oren & Shai (1997), which stipulates that hydrophobicity and charge are the primary determinants of antimicrobial activities of AMPs. The same observation was made by a number of research and review articles (Čeřovský et al, 2008; Li et al, 2016; Toro Segovia et al, 2017) where all of which made the observation that positive charge and amphipahicity was important for AMP antimicrobial activity. In fact, positive charge is a key recognition feature of AMPs and antimicrobial activity could be significantly increased by simply adding more positively charged amino acids to the peptides (Papo & Shai, 2003).…”

Peer Review #2 of "Toward insights on determining factors for high activity in antimicrobial peptides via machine learning (v0.2)"

“…The observation made in this study is consistent with previous experimental results of Oren and Shai (1997), which stipulates that hydrophobicity and charge are the primary determinants of antimicrobial activities of AMPs. The same observation was made by a number of research and review articles (Čeřovský et al, 2008;Li et al, 2016;Toro Segovia et al, 2017) where all of which made the observation that positive charge and amphipahicity was important for AMP antimicrobial activity. In fact, positive charge is a key recognition feature of AMPs and antimicrobial activity could be significantly increased by simply adding more positively charged amino acids to the peptides (Papo and Y, 2003).…”

Insect Cecropins, Antimicrobial Peptides with Potential Therapeutic Applications

“…In the domesticated silkworm Bombyx mori , the Cec gene family is composed of at least 14 elements (two Cec A ( A1 and A2 ), six Cec B ( B1 – B6 ), one Cec C , two Cec D ( D and D2 ), one Cec E , and two enbocins ( enb 1 and 2)), organized in two clusters, mapping on two different chromosomes [72]. In Coleoptera, functional Cec genes have been identified in species like Acalolepta luxuriosa (Cec; [20]), Oxysternon conspicillatum (Oxysterlins; [19]), and Paederus dermatitis (Sarcotoxin Pd; [21]), whereas only non-functional Cec pseudogenes have been reported in the coleopteran model Tribolium castaneum [73,74].…”