Functional Modulation of Peptide Structural Interaction Fingerprints upon Stereochemical Diversification

The total conformational search space of an l-amino acid
in a polypeptide chain is limited to 21% with structural variation
including helices, sheets, turns, and random coils. The conformational
search space of a polypeptide will expand to astronomical propositions
if both l- and d-chiral amino acids are used to
design novel polypeptide chains with altogether new structures and
functions. This possibility has been systematically investigated in
this study by making designed mutations that result in novel architectures.
We hypothesize that the electrostatic interaction fingerprints of
these peptides are distinctly different with stereochemical mutations
of the polypeptide chain, and this will consequently reflect in their
ability to interact and penetrate the membrane. The designed peptide
structures are examined for their ability to interact with bacterial
and mammalian cell membranes by employing molecular dynamics simulations.
Mammalian triple-negative breast cancer (MDA-MB-231) and noncancerous
(MCF-10A) cell lines were treated with 5(6)-carboxyfluorescein-labeled
peptides, and the cellular uptake was measured quantitatively by flow
cytometry for objective comparison of their ability to be used as
anticancer or drug delivery agents. Antibacterial properties of the
peptides were tested for Gram-positive Staphylococcus
aureus (S. aureus)
and Gram-negative Escherichia coli (E. coli) species. Both in silico and in vitro experimental results are largely
supportive of the hypothesis tested, and they further point to the
possibility of expanding the polypeptide conformational space in the
search for novel functional molecular constructs. Our study also identified
two promising therapeutic peptides for further development: YRC03
as a viable antibacterial agent against Gram-negative bacteria and
YRC01 as a promising drug delivery vehicle for breast cancer treatment.