Chemical synthesis and biological activity of a novel antibacterial peptide deduced from a pig myeloid cDNA

Abstract

Several myeloid precursors of antibacterial peptides have recently been shown to share homologous pre-and pro-regions. Taking advantage of this homology, a novel cDNA was cloned from pig bone marrow RNA. This encodes a 166-residue polypeptide with highly conserved pre-(29 residues) and pro-(101 residues) sequences, followed by a unique, 36-residue C-terminal sequence. Structure analyses of this C-terminal region have identified a highly cationic sequence predicted to adopt an amphipathic a-helical conformation. A peptide corresponding to this sequence was chemically synthesized and shown to arrest the growth of both Gram-positive and Gram-negative bacteria. At least for Escherichia coli, the activity of this peptide appears to be mediated by its ability to permeabilize the bacterial membranes.

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

“…Peptides corresponding to all known sequences have either been purified from natural sources [13,[34][35][36][37][38][39], after processing of the respective precursors, or have been obtained by chemical synthesis based on the sequence deduced from cDNA [26,27,29,32,33]. At present they include rabbit CAPI8(106 142) [39], human FALL-39/CAP18 [32,33], PMAP-36 [26] and PMAP-37 [29], all of which are mostly s-helical; two Trpcontaining peptides, indolicidin [36] and PMAP-23 [27]; the Pro-and Arg-rich Bac5 [12], Bac7 [12], PR-39 [13] and prophenin [38]; the cyclic dodecapeptide [34] and protegrins [37] which are loop-forming molecules with one and two disulfide bonds, respectively. The sequence of the Pro-and Arg-rich peptides (Fig.…”

“…1) is peculiar in that several short modules are present, and often arranged in tandem repeats [12,13,38]. The structure of some of these peptides has been analyzed by circular dichroism spectroscopy, showing that PMAP-36 [26], PMAP-37 [29] and FALL-39 [32] undergo a transition from a random coil to an ordered, mainly s-helical conformation on addition of an organic solvent. This behaviour indicates the presence of an amphipathic s-helical conformation, a structure found in many membrane-active peptides.…”

“…The Pro-and Arg-rich peptides are substantially more active against gram-negative than gram-positive bacteria [13,35,38]. Conversely, the other linear (helical and Trp-rich) and Cys-containing peptides are in general highly active against both gram-positive and gramnegative microorganisms [26,27,32,34,36,37,49]. Protegrins also exhibit fungicidal activity [37], while Bac5 and Bac7 kill leptospirae [50].…”

“…Many of them have been shown to rapidly permeabilize the membranes of susceptible bacteria [14,26,27,29,51]. The Pro-and Arg-rich Bac5 and Bac7 inhibit incorporation of precursor molecules into protein and RNA [14] and PR-39 has been shown to stop protein and DNA synthesis in gram-negative bacteria [52].…”

Role of intestinal epithelial cells in the innate immune defence of the pig intestine

“…PR-39 was isolated originally from bulk homogenates of porcine small intestines [2] but further studies demonstrated that this cathelicidin was derived from neutrophils and not from intestinal epithelia [68]. PR-39 is active mainly against gram-negative bacteria [2,63] and increases significantly in pig sera during the onset of salmonellosis [76].…”