Antimicrobial and pore-forming peptides of free-living and potentially highly pathogenic Naegleria fowleri are released from the same precursor molecule.
The pore-forming polypeptides of Naegleria fowleri, naegleriapores A and B, are processed from separate multipeptide precursor structures. According to their transcripts, each precursor molecule appears to contain additional naegleriapore-like polypeptides, all of which share a structural motif of six invariant cysteine residues within their amino acid sequence. To identify the putative pronaegleriapore-derived peptides at the protein level, amoebic extracts were screened for small cysteine-rich polypeptides by fluorescently labeling their cysteine residues. Three novel naegleriapore isoforms derived from the precursor molecule of naegleriapore B were identified. Two of the isoforms were purified to homogeneity and tested for their biological activity. The pore-forming activity of the novel peptides was remarkably lower than that of the originally isolated naegleriapores, but both peptides killed bacteria by permeabilizing their cytoplasmic membranes. Collectively, these results indicate that naegleriapore isoforms with antibacterial and pore-forming activity are proteolytically released from the same precursor protein, presumably to generate a phylogenetically ancient complementary antimicrobial arsenal.
Herbst
Rosa
R
Department of Special Zoology, Ruhr-University of Bochum, Universitatsstrasse 150, 44780 Bochum, Germany.
Marciano-Cabral
Francine
F
Leippe
Matthias
M
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000737:chemistry; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008969:Molecular Sequence Data; D016848:Naegleria fowleri / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism*; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
D000890:Anti-Infective Agents; D010455:Peptides; D020033:Protein Isoforms; D012333:RNA, Messenger; D003545:Cysteine