Edited by: Maria Luisa Mangoni, Sapienza University of Rome, Italy
Reviewed by: Dr. Anirban Bhunia, Bose Institute, India; Mare Cudic, Florida Atlantic University, USA
*Correspondence: Mohammed A. Hossain
Frances Separovic
John D. Wade
This article was submitted to Chemical Biology, a section of the journal Frontiers in Chemistry
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The increasing widespread onset of bacterial multi-drug resistance, associated with major clinical pathogenic infections, has resulted in calls for the development new antimicrobial agents (Laxminarayan et al.,
The peptide, Chex1-Arg20, was
The discontinuous dimer of Chex1-Arg20, A3-APO, was shown in
Nine-Fluorenylmethoxylcarbonyl (Fmoc)-L-amino acids, 2-(6-chloro-1H-benzotriazole-1-yl)-1,1,3,3-tetramethylamonium hexafluorophosphate (HCTU), and 1-[Bis(dimethylamino) methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxid (HATU) were from GL Biochem (Shanghai, China). TentaGel-MB-RAM-resin was from Rapp Polymere (Tubingen, Germany). Nα-Fmoc-Nα-methyl-L-arginine(Nω-Pbf), and Nα-Fmoc-D-arginine(D-Pbf) were purchased from Novabiochem (Sydney, Australia). N,N-Diisopropylethylamine (DIPEA), dimethylformamide (DMF), and trifluoroacetic acid (TFA) were obtained from Auspep (Melbourne, Australia). Piperidine, triisopropylsilane (TIPS), anisole, and acetonitrile (CH3CN) were all obtained from Sigma (Sydney, Australia).
The peptides were synthesized by Fmoc/tBu solid-phase methods (Fields and Noble,
An antibacterial assay was undertaken to determine the minimal inhibitory concentration (MIC) as described previously (Li et al.,
The proliferation of HEK-293 (ATCC® CRL-1573™) and H-4-II-E (ATCC® CRL-1548™) cells were tested with the Chex1-Arg20 analogs using the CellTiter 96 AQueous Non-Radioactive Cell Proliferation Assay (Promega) as described previously (Li et al.,
Peptide
Chex1-Arg20 | Chex-RPDKPRPYLPRPRPPRPVR-NH2 | 2475.0 | 2476.8 | |
DR7 | Chex-RPDKP r PYLPRPRPPRPVR-NH2 | 2474.9 | 2474.8 | |
DR7(1–19) | RPDKP r PYLPRPRPPRPV-NH2 | 2318.8 | 2319.3 | |
DR7(7–19) | r PYLPRPRPPRPV-NH2 | 1600.1 | 1603.0 | |
Chex1-Val19 | Chex-RPDKP r PYLPRPRPPRPV-NH2 | 2318.8 | 2319.2 | |
DR20 | Chex-RPDKPRPYLPRPRPPRPV r-NH2 | 2474.9 | 2475.2 | |
mR20 | Chex-RPDKPRPYLPRPRPPRPVmR-NH2 | 2489.0 | 2488.9 | |
reverse | Chex-RVPRPPRPRPLYPRPKDPR-NH2 | 2475.0 | 2478.0 |
Each Chex1-Arg20 analog was assayed against the nosocomial Gram-negative bacterium
0.8 ± 0.1 |
>100 | >100 | >100 | 36.1 ± 0.6 | 11.8 ± 0.1 | 14.5 ± 0.1 | >100 |
>100 μM | >100 μM | |
>100 μM | >100 μM | |
>100 μM | >100 μM | |
>100 μM | >100 μM | |
>100 μM | >100 μM | |
>100 μM | >100 μM | |
>100 μM | >100 μM | |
>100 μM | >100 μM |
In summary, a series of D-amino acid substituted analogs of the PrAMP, Chex1-Arg20, were prepared by standard Fmoc/tBu solid phase peptide synthesis. These analogs were tested against the Gram-negative bacterium
WL performed chemical syntheses, antibacterial assay and drafted the manuscript; ZS performed cytotoxicity test; NO, LO, ER, MH, FS, and JW took part in experimental design. All authors worked on the manuscript.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
We gratefully acknowledge support of the studies undertaken in the authors' laboratory by ARC Discovery Project grants (DP150103522) to JW and MH, and NHMRC Project grants (APP1029878) to NMOBS and (APP1008106) to ER and NMOBS. JW is an NHMRC (Australia) Principal Research Fellow. WL is the recipient of an MIRS PhD award and Dr Albert Shimmins Postgraduate Writing-Up award (University of Melbourne). Research at the FINMH was also supported by the Victorian Government's Operational Infrastructure Support Program.