Structure-activity study of oncocin: On-resin guanidinylation and incorporation of homoarginine, 4-hydroxyproline or 4,4-difluoroproline residues
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Structure-activity study of oncocin : On-resin guanidinylation and incorporation of homoarginine, 4-hydroxyproline or 4,4-difluoroproline residues. / Shaikh, Ashif Y.; Björkling, Fredrik; Zabicka, Dorota; Tomczak, Magdalena; Urbas, Malgorzata; Domraceva, Ilona; Kreicberga, Agrita; Franzyk, Henrik.
In: Bioorganic Chemistry, Vol. 141, 106876, 2023.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Structure-activity study of oncocin
T2 - On-resin guanidinylation and incorporation of homoarginine, 4-hydroxyproline or 4,4-difluoroproline residues
AU - Shaikh, Ashif Y.
AU - Björkling, Fredrik
AU - Zabicka, Dorota
AU - Tomczak, Magdalena
AU - Urbas, Malgorzata
AU - Domraceva, Ilona
AU - Kreicberga, Agrita
AU - Franzyk, Henrik
N1 - Publisher Copyright: © 2023 The Authors
PY - 2023
Y1 - 2023
N2 - Antimicrobial peptides (AMPs) often display guanidinium functionalities, and hence robust synthetic procedures are needed to facilitate access to analogues with unnatural homologues of arginine (Arg = 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 Arg → 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-Arg → 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 Pro → Dfp modifications proved to possess the best activity profile: MICs of 1–2 µg/mL against E. coli and Klebsiella pneumoniae, less than 1% hemolysis at 800 µg/mL, and an IC50 above 1280 µg/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.
AB - Antimicrobial peptides (AMPs) often display guanidinium functionalities, and hence robust synthetic procedures are needed to facilitate access to analogues with unnatural homologues of arginine (Arg = 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 Arg → 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-Arg → 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 Pro → Dfp modifications proved to possess the best activity profile: MICs of 1–2 µg/mL against E. coli and Klebsiella pneumoniae, less than 1% hemolysis at 800 µg/mL, and an IC50 above 1280 µg/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.
KW - 4,4-Difluoroproline
KW - Antibacterial activity
KW - On-resin guanidinylation
KW - Oncocin
KW - Stability to enzymes
KW - Structure-activity relationships
KW - Trans-4-Hydroxy-L-proline
U2 - 10.1016/j.bioorg.2023.106876
DO - 10.1016/j.bioorg.2023.106876
M3 - Journal article
C2 - 37797458
AN - SCOPUS:85173093853
VL - 141
JO - Bioorganic Chemistry
JF - Bioorganic Chemistry
SN - 0045-2068
M1 - 106876
ER -
ID: 370476005