Secondary Structure and Membrane Interaction of PR‐39, a Pro+Arg‐rich Antibacterial Peptide

Abstract

PR‐39 is a 4719‐Da peptide isolated from pig intestine and belonging to the recently discovered family of Pro + Arg‐rich antibacterial peptides. PR‐39 does not lyse Escherichia coli, instead the lethal action is probably linked to the termination of DNA and protein synthesis [Boman, H. G., Agerberth, B. & Boman, A. (1993) Infect. Immun. 61, 2978–2984]. Circular dichroism and Fourier‐transform infrared spectroscopy have been used to investigate the secondary structure of PR‐39 in the absence or presence of lipids. According to the circular dichroic data, this structure is not altered upon incubation of PR‐39 with negatively charged vesicles, although the infrared spectra suggest that the hydrogen bond pattern is modified upon the peptide—lipid interaction. This is detected by a shift in the maximum wavelength of absorption of PR‐39 from 1636 cm−1 in the absence of lipids to 1645 cm−1 in the presence of lipids. We have further addressed the question of the possible mechanism of interaction of PR‐39 with model membranes (liposomes and planar lipid bilayers) whose lipid compositions mimick that of the E. coli inner membrane. PR‐39 induced a calcein release from large unilamellar vesicles, which is dependent upon the peptide concentration and upon the presence of negatively charged lipid (glycerophosphoglycerol) in the membrane. The binding study of PR‐39 to dioleoylglycerophosphoglycerol vesicles suggests that nearly 100% of the added peptide is membrane‐bound. Addition of PR‐39 to a planar lipid bilayer induced a linear increase in the current but no channel formation was observed since no discrete steps of conductance occurred.

Granulysin, a T Cell Product, Kills Bacteria by Altering Membrane Permeability

“…These two species of proteins include 1) small peptides (typically 16 -40 aa), e.g., magainins, cecropins, defensins, protegrins, and tachyplesins (8,17,24,25); and 2) larger proteins with multiple ␣ helical domains, e.g., amoebapores, porcine NK-lysin, and human granulysin (16,26). All these proteins are cationic amphipathic species whose basic residues are thought to interact with the negatively charged membrane.…”

“…The antimicrobial activity of these peptides is dependent on their ability to form multimers that facilitate pore formation leading to cell death (6). In addition, most antimicrobial peptides are cationic, although amino acid usage varies, including arginine, histidine, and lysine (7,8). The putative structure of granulysin is a four ␣ helical bundle similar to the amoebapore family members (3).…”

Cathelicidins: a novel protein family with a common proregion and a variable C‐terminal antimicrobial domain

“…This behaviour indicates the presence of an amphipathic s-helical conformation, a structure found in many membrane-active peptides. A polyproline type structure has been suggested for PR-39 [48] and, based on sequence similarity, such a structure might also occur in Bac5 and Bac7, although this still requires confirmation.…”

Porcine antimicrobial peptides: New prospects for ancient molecules of host defense

“…Structure prediction analysis and circular dichroism spectra suggest that PMAP-36, and -37 adopt an amphipathic α-helix, whereas PMAP-23 assumes a hairpin-like structure (an antiparallel β-sheet connected by a loop at center). Sequence comparison reveals that PMAP-23 shows no significant similarity to any known AMPs, whereas PMAP-36 (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) has a moderate homology of 35% to a rabbit cathelicidin CAP18. Although PMAP-37 shows negligible identity to porcine cecropin P1, it has more than 50% similarity to two insect AMPs, cecropins A and B.…”

“…proline-arginine-rich peptide PR-39 is a linear cathelicidin of 39 amino acid residues with high contents of proline (49%) and arginine (26%) adopting a polyproline type II structure [1,19]. It was isolated originally from bulk homogenates of porcine small intestines [1], but later cloning of PR-39 cDNA in myeloid cells from porcine bone marrow suggested that the enteric PR-39 may be derived from resident leukocytes in the intestine rather than from intestinal epithelia [112].…”