Structure-activity study of oncocin: On-resin guanidinylation and incorporation of homoarginine, 4-hydroxyproline or 4,4-difluoroproline residues.
Bioorg Chem
; 141: 106876, 2023 12.
Article
em En
| MEDLINE
| ID: mdl-37797458
ABSTRACT
Antimicrobial peptides (AMPs) often display guanidinium functionalities, and hence robust synthetic procedures are needed to facilitate access to analogues with unnatural homologues of arginine (Argâ¯=â¯R). Initially, a resin-bound Arg/Pro-rich fluoren-9-yl-methyloxycarbonyl-protected fragment (Fmoc-RPRPPR) of the AMP oncocin (i.e., VDKPPYLPRPRPPRRIYNR-NH2) was employed in a comparative on-resin assessment of commercial guanidinylation reagents head-to-head with the recently studied bis-Boc-protected triazole-based reagent, 1H-triazole-1-[N,N'-bis(tert-butoxycarbonyl)]-carboxamidine, which was synthesized by a chromatography-free procedure. This reagent was found to enable quantitative conversion in solid-phase peptide synthesis (SPPS) of peptides displaying homoarginine (Har) residues and/or an N-terminal guanidinium group. SPPS was used to obtain analogues of the 18-mer oncocin with single as well as multiple Argâ¯ââ¯Har modifications. In addition, the effect of replacement of proline (Pro) residues in oncocin was explored by incorporating single or multiple trans-4-hydroxy-l-proline (Hyp) or 4,4-difluoro-l-proline (Dfp) residues, which both affected hydrophobicity. The resulting peptide library was tested against both Gram-negative and Gram-positive bacteria. Analysis of the minimal inhibitory concentrations (MICs) showed that analogues, displaying modifications at positions 4, 5 and 12 (originally Pro residues), had retained or slightly improved antimicrobial activity. Next, an oncocin analogue with two stabilizing l-Argâ¯ââ¯d-Arg replacements in the C-terminal part was further modified by triple-replacement of Pro by either Dfp or Hyp in positions 4, 5, and 12. The resulting analogue displaying three Proâ¯ââ¯Dfp modifications proved to possess the best activity profile MICs of 1-2⯵g/mL against E. coli and Klebsiella pneumoniae, less than 1% hemolysis at 800⯵g/mL, and an IC50 above 1280⯵g/mL in HepG2 cells. Thus, incorporation of bis-fluorinated Pro residues appears to constitute a novel tool in structure-activity studies aimed at optimization of Pro-rich AMPs.
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Base de dados:
MEDLINE
Assunto principal:
Escherichia coli
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Homoarginina
Idioma:
En
Revista:
Bioorg Chem
Ano de publicação:
2023
Tipo de documento:
Article
País de afiliação:
Emirados Árabes Unidos