Hornerin contains a Linked Series of Ribosome-Targeting Peptide Antibiotics

Ulrich Gerstel,Joachim Bartels,Alexander Becker,Andreas Tholey,Jens-Michael Schröder,Ties Latendorf

doi:10.1038/s41598-018-34467-8

Abstract

Cationic intrinsically disordered antimicrobial peptides (CIDAMPs) belong to a novel class of epithelial peptide antibiotics with microbicidal activity against various pathogens, including Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Candida albicans. Here we show that treatment of distinct bacteria with different hornerin (HRNR)-derived CIDAMPs cause formation of unique cytoplasmic protein aggregates, suggesting a common intracellular mode of action. We further found that, unlike most amphipathic antimicrobial peptides, HRNR traverses bacterial membranes energy-dependently and accumulates within the cytoplasm. Strikingly, certain structurally different, HRNR-based CIDAMPs were found to bind to an identical panel of distinct bacterial ribosomal proteins, thereby manifesting features of several known classes of antibiotics. This may cause the formation of aberrant proteins and toxic protein aggregates in HRNR-treated pathogens which eventually may induce its death. Our study reveals evidence that structurally distinct CIDAMPs of an abundant body surface protein simultaneously target multiple sites of the bacterial protein synthesis machinery.

Highlights

By unknown reasons, healthy human skin is remarkably resistant towards infection by Pseudomonas (P.) aeruginosa, an environmental opportunistic pathogen widespread in water and soil
Our findings clearly show that distinct HRNR-derived Cationic intrinsically disordered antimicrobial peptides (CIDAMPs) exert bactericidal activity in E. coli by targeting the ribosome
The most intensive 37 kDa band seen upon HRNR-Far-Western blot analyses (Fig. 6) originated from E. coli 50S ribosomal protein L2

Summary

Discussion

Our findings clearly show that distinct HRNR-derived CIDAMPs exert bactericidal activity in E. coli by targeting the ribosome. We surmise that CIDAMPs, by manifesting the features of several known classes of ribosome inhibiting antibiotics by simultaneously blocking the ribosome assembly, the peptidyl transferase center and the peptide-exit tunnel of the ribosome, and by targeting simultaneously multiple other ribosomal proteins, may cause the synthesis of aberrant and toxic proteins forming large disordered aggregates[12] in CIDAMP-treated bacteria (Fig. 1 and Supplementary Figs S1–S3). In support with our findings, ultrastructural analyses of aminoglycoside-treated P. aeruginosa shows marked electron-dense cytosolic aggregates (Fig. 7), very similar as seen upon challenge with almost all CIDAMPs we had studied (Fig. 1 and Supplementary Figs S1–S3) Since these aggregates are indicative for protein misfolding or assembly of misfolded polypeptides into insoluble and cytotoxic aggregates, known to be able to induce the bacterial death[12], it is tempting to speculate that CIDAMPs, at least in part, are killing microbes in a self-assembly nanostructure-dependent manner. The precise chain of events that leads to CIDAMP-dependent cell death in bacteria and C. albicans remains to be elucidated, the ability of CIDAMPs to elicit antimicrobial activity via protein aggregate-formation in bacteria represents a rich and unexplored chemical space to be mined in search of novel therapeutic strategies to fight infectious diseases[12]

Methods

Author Contributions

Findings

Additional Information