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Antimicrob Agents Chemother. 2016 May 23;60(6):3687-99. doi: 10.1128/AAC.02341-15. Print 2016 Jun.

Single Amino Acid Substitutions at Specific Positions of the Heptad Repeat Sequence of Piscidin-1 Yielded Novel Analogs That Show Low Cytotoxicity and In Vitro and In Vivo Antiendotoxin Activity.

Author information

1
Molecular and Structural Biology Division, CSIR-Central Drug Research Institute, Lucknow, India.
2
Electron Microscopy Unit, CSIR-Central Drug Research Institute, Lucknow, India.
3
Sophisticated Analytical Instrumentation Facility, CSIR-Central Drug Research Institute, Lucknow, India.
4
Molecular and Structural Biology Division, CSIR-Central Drug Research Institute, Lucknow, India Academy of Scientific and Innovative Research, Chennai, India.
5
Electron Microscopy Unit, CSIR-Central Drug Research Institute, Lucknow, India Academy of Scientific and Innovative Research, Chennai, India.
6
Molecular and Structural Biology Division, CSIR-Central Drug Research Institute, Lucknow, India Academy of Scientific and Innovative Research, Chennai, India jk_ghosh@cdri.res.in.

Abstract

Piscidin-1 possesses significant antimicrobial and cytotoxic activities. To recognize the primary amino acid sequence(s) in piscidin-1 that could be important for its biological activity, a long heptad repeat sequence located in the region from amino acids 2 to 19 was identified. To comprehend the possible role of this motif, six analogs of piscidin-1 were designed by selectively replacing a single isoleucine residue at a d (5th) position or at an a (9th or 16th) position with either an alanine or a valine residue. Two more analogs, namely, I5F,F6A-piscidin-1 and V12I-piscidin-1, were designed for investigating the effect of interchanging an alanine residue at a d position with an adjacent phenylalanine residue and replacing a valine residue with an isoleucine residue at another d position of the heptad repeat of piscidin-1, respectively. Single alanine-substituted analogs exhibited significantly reduced cytotoxicity against mammalian cells compared with that of piscidin-1 but appreciably retained the antibacterial and antiendotoxin activities of piscidin-1. All the single valine-substituted piscidin-1 analogs and I5F,F6A-piscidin-1 showed cytotoxicity greater than that of the corresponding alanine-substituted analogs, antibacterial activity marginally greater than or similar to that of the corresponding alanine-substituted analogs, and also antiendotoxin activity superior to that of the corresponding alanine-substituted analogs. Interestingly, among these peptides, V12I-piscidin-1 showed the highest cytotoxicity and antibacterial and antiendotoxin activities. Lipopolysaccharide (12 mg/kg of body weight)-treated mice, further treated with I16A-piscidin-1, the piscidin-1 analog with the highest therapeutic index, at a single dose of 1 or 2 mg/kg of body weight, showed 80 and 100% survival, respectively. Structural and functional characterization of these peptides revealed the basis of their biological activity and demonstrated that nontoxic piscidin-1 analogs with significant antimicrobial and antiendotoxin activities can be designed by incorporating single alanine substitutions in the piscidin-1 heptad repeat.

PMID:
27067326
PMCID:
PMC4879410
DOI:
10.1128/AAC.02341-15
[Indexed for MEDLINE]
Free PMC Article

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