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Dimerization and lysine substitution of melittin have differing effects on bacteria

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posted on 2024-10-31, 03:01 authored by Tamara Matthyssen, Wenyi LiWenyi Li, James A Holden, Jason C Lenzo, Sara Hadjigol, Neil M O’Brien-Simpson

Introduction: Melittin is a potent antimicrobial peptide from bee venom that is effective against both Gram-positive and Gram-negative bacteria. However, it is extremely toxic to mammalian cells and, as yet, has no clinical use. Modifications to its amino acid sequence, cyclization, truncation, and dimerization have been attempted in order to reduce its toxicity whilst maintaining its antimicrobial activity. Methods: In this study, we targeted the three lysine residues present in melittin and substituted them with lysine homologs containing shorter side chains (ornithine, Orn, diaminobutyric acid, Dab, and diaminopropanoic acid, Dap) and made both parallel and antiparallel melittin dimers to observe how lysine substitution and dimerization affects its activity and toxicity. The antibacterial activity of melittin and its analogs was tested against S. aureus (Gram-positive bacteria) and E. coli (Gram-negative bacteria), and cytotoxicity was tested against the mammalian cell lines HEK293 and H4IIE. Results: Overall, dimerization and lysine substitution exhibited improved antimicrobial activity toward E. coli and limited improvement toward S. aureus. However, mammalian cell toxicity was only marginally reduced compared to native melittin. Interestingly, the parallel dimer was found to be marginally more active than the antiparallel dimer, indicating orientation maybe important for activity, although both dimers were less effective than the native and Lys-analog peptides toward S. aureus. Of the Lys substitutions, Dab and Dap improved melittin’s activity toward E. coli. Discussion: Dimerization and Lys substitution of melittin improved the antimicrobial activity toward Gram-negative bacteria but did not significantly improve its activity toward Gram-positive bacteria. Some analogs also displayed reduced toxicity toward HEK293 and H4IIE cells but overall remained toxic at bactericidal concentrations. Our data indicates that although highly antibacterial, melittin’s toxicity is the major drawback in its potential use.

Funding

The National Health and Medical Research Council (NHMRC) of Australia and the Australian Research Council (ARC) are thanked for financial support over many years for the peptide chemistry and chemical biology studies reported in the authors’ laboratories. NMOS is the recipient of NHMRC funding (APP1142472, APP1158841, and APP1185426), ARC funding (DP210102781, DP160101312, and LE200100163), Cancer Council Victoria funding (APP1163284), and Australian Dental Research Funding in antimicrobial materials, and research is supported by the Centre for Oral Health Research at The Melbourne Dental School.

History

Publication Date

2024-10-07

Journal

Frontiers in Pharmacology

Volume

15

Article Number

1443497

Pagination

13p.

Publisher

Frontiers Media S.A.

ISSN

1663-9812

Rights Statement

© 2024 Matthyssen, Li, Holden, Lenzo, Hadjigol and O’Brien-Simpson. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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