Structure Elucidation and Functional Studies of a Novel β-hairpin Antimicrobial Peptide from the Marine Polychaeta Capitella teleta

Abstract

Endogenous antimicrobial peptides (AMPs) are evolutionary ancient molecular factors of innate immunity that play a key role in host defense. Among the most active and stable under physiological conditions AMPs are the peptides of animal origin that adopt a β-hairpin conformation stabilized by disulfide bridges. In this study, a novel BRICHOS-domain related AMP from the marine polychaeta Capitella teleta, named capitellacin, was produced as the recombinant analogue and investigated. The mature capitellacin exhibits high homology with the known β-hairpin AMP family—tachyplesins and polyphemusins from the horseshoe crabs. The β-hairpin structure of the recombinant capitellacin was proved by CD and NMR spectroscopy. In aqueous solution the peptide exists as monomeric right-handed twisted β-hairpin and its structure does not reveal significant amphipathicity. Moreover, the peptide retains this conformation in membrane environment and incorporates into lipid bilayer. Capitellacin exhibits a strong antimicrobial activity in vitro against a wide panel of bacteria including extensively drug-resistant strains. In contrast to other known β-hairpin AMPs, this peptide acts apparently via non-lytic mechanism at concentrations inhibiting bacterial growth. The molecular mechanism of the peptide antimicrobial action does not seem to be related to the inhibition of bacterial translation therefore other molecular targets may be assumed. The reduced cytotoxicity against human cells and high antibacterial cell selectivity as compared to tachyplesin-1 make it an attractive candidate compound for an anti-infective drug design.

Total Synthesis of Novel Antimicrobial β-Hairpin Capitellacin Via Rapid Flow-Based SPPS Assembly and Regioselective On-Resin Disulfide Cyclisation

“…The most recent of these is a 20 residue peptide, capitellacin (1), initially predicted (in 2014) from the genomic data of Capitella teleta, aided by a Basic Local Alignment Search (BLAST) of the genome sequence, based on the similarity of its BRICHOS domain and pro-region to previously isolated marine polychaetes AMPs (Panteleev et al 2018;Tasiemski et al 2014). More recently, Panteleev et al (2020) produced capitellacin (1) recombinantly in Escherichia coli and performed a thorough elucidation of its structure and activity (Panteleev et al 2020). Nuclear magnetic resonance (NMR) studies revealed capitellacin (1) to exist as a monomeric antiparallel β-hairpin (type IV β-turn) structure in solution, stabilised by two parallel disulfide bonds, showing significant sequence homology to the extensively studied and potent β-hairpin AMP, tachyplesin I (2) (Fig.…”

Marine Organisms as a Rich Source of Biologically Active Peptides

“…Analysis of the antimicrobial activity of capitellacin demonstrated that this peptide has broad-spectrum activity, but it was up to eightfold lower than that of tachyplesin-1 (a peptide from the tachyplesins family). Unlike other peptides with β-hairpin structure, capithelinacin was inefficient in breaking the cytoplasmic membrane and inhibiting bacterial translation, suggesting other mechanisms of action and targets (Panteleev et al, 2020).…”

Marine Peptides: Structure, Bioactivities, and a New Hope for Therapeutic Application

“…Papers included in this Special Issue deal with marine polychaeta, providing good examples of their biological potential. The peptides arenicins and capitellacin, were isolated from Arenicola marina [ 16 ] and Capitella teleta [ 17 ], respectively. Earlier, structure-function relationships of arenicins have been extensively investigated [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ].…”

“…Besides, this approach promotes antimicrobial effects, taking into account the inhibited complement system [ 26 ]. In this Special Issue, a novel BRICHOS-domain related AMP from the marine polychaeta Capitella teleta , named capitellacin, was reported [ 17 ]. The peptide exhibits high homology with β-hairpin marine peptides tachyplesins and polyphemusins from the horseshoe crabs.…”

“…Molecular mechanism of the peptide antimicrobial action does not seem to be related to the inhibition of bacterial translation. A low cytotoxicity towards human cells and high antibacterial cell selectivity as compared to tachyplesin-1 make capitellacin a promising candidate compound for design of a novel anti-infective drug [ 17 ].…”