posted on 2020-08-17, 21:29authored byTripti Kumari, Devesh Pratap Verma, Tayyaba Afshan, Neeraj Kumar Verma, Garima Pant, Mehmood Ali, P. K. Shukla, Kalyan Mitra, Jimut Kanti Ghosh
Cytotoxic frog antimicrobial peptide
Temporin L (TempL) is an attractive
molecule for the design of lead antimicrobial agents due to its short
size and versatile biological activities. However, noncytotoxic TempL
variants with desirable biological activities have rarely been reported.
TempL analogue Q3K,TempL is water-soluble and possesses a significant
antiendotoxin property along with comparable cytotoxicity to TempL.
A phenylalanine residue, located at the hydrophobic face of Q3K,TempL
and the “d” position of its phenylalanine zipper sequence,
was replaced with a cationic lysine residue. This analogue, Q3K,F8K,TempL,
showed reduced hydrophobic moment and was noncytotoxic with lower
antimicrobial activity. Interestingly, swapping between tryptophan
at the fourth and serine at the sixth positions turned Q3K,F8K,TempL
totally amphipathic as reflected by its helical wheel projection with
clusters of hydrophobic and hydrophilic residues and the highest hydrophobic
moment among these peptides. Surprisingly, this analogue, SW,Q3K,F8K,TempL,
was as noncytotoxic as Q3K,F8K,TempL but showed augmented antimicrobial
and antiendotoxin properties, comparable to that of TempL and Q3K,TempL.
SW,Q3K,F8K,TempL exhibited appreciable survival of mice against P. aeruginosa infection and a lipopolysaccharide (LPS)
challenge. Unlike TempL and Q3K,TempL, SW,Q3K,F8K,TempL adopted an
unordered secondary structure in bacterial membrane mimetic lipid
vesicles and did not permeabilize them or depolarize the bacterial
membrane. Overall, the results demonstrate the design of a nontoxic
TempL analogue that possesses clusters of hydrophobic and hydrophilic
residues with impaired secondary structure and shows a nonmembrane-lytic
mechanism and in vivo antiendotoxin and antimicrobial
activities. This paradigm of design of antimicrobial peptide with
clusters of hydrophobic and hydrophilic residues and high hydrophobic
moment but low secondary structure could be attempted further.