Structure-Activity Relationship of the N-terminal Helix Analog of Papiliocin, PapN

Abstract

Papiliocin, from the swallowtail butterfly, Papilio xuthus, shows high bacterial cell selectivity against Gram-negative bacteria. Recently, we designed a 22mer analog with N-terminal helix from Lys 3 to Ala 22 , PapN. It shows outstanding antimicrobial activity against Gram-negative bacteria with low toxicity against mammalian cells. In this study, we determined the 3-D structure of PapN in 300 mM DPC micelle using NMR spectroscopy and investigated the interactions between PapN and DPC micelles. The results showed that PapN has an amphipathic α-helical structure from Lys 3 to Lys 21 .STD-NMR and DOSY experiment showed that this helix is important in binding to the bacterial cell membrane. Furthermore, we tested antibacterial activities of PapN in the presence of salt for therapeutic application. PapN was calcium-and magnesium-resistant in a physiological condition, especially against Gram-negative bacteria, implying that it can be a potent candidate as peptide antibiotics.

Structure-Activity Relationships of Peptide Antibiotics with Improved Bacterial Cell Selectivity of Pseudin

“…12, 13 We analyzed the tertiary structure of Ps-4K-P and compared it with that of parent peptide Ps. Ps in DPC micelles has amphipathic -helical structure from Leu 2 to Val 24 orientating hydrophobic side chains toward one side, and the hydrophilic side chins toward the other side (Fig.…”

“…The 1 H chemical shift deviation was referenced according to the method of Wishart et al 12 In the case of Ps-4K-P, residues from Ile 12 to the C-terminus have a negative 1 Hα Chemical Shift Index (CSI) as well as small 3 J HN coupling constants which imply that it has a stable -helix structure in this region. Rmsd from the mean structure Backbone atoms of all residues 1.8990.61 All heavy atoms of all residues 2.6680.96 Backbone atoms of residues (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) 0.5040.21 All heavy atoms of residues (11-24) 1.2710.20 a E NOE , E tor and E repel are the energies related to the NOE violations, the torsion angle violations, and the van der Waals repulsion term, respectively. The value of the square-well NOE (E NOE ) and torsion angle (E tor ) potentials were calculated with force constants of 50 kcal mol -1 Å -2 and 200 kcal mol -1 rad -2 , respectively.…”