title: Primary and secondary structure of the pore-forming peptide of pathogenic Entamoeba histolytica.
abstract: A pore-forming peptide is implicated in the potent cytolytic activity of pathogenic Entamoeba histolytica. Using NH2-terminal sequence information of this peptide, the corresponding cDNA was isolated. The cDNA-deduced amino acid sequence revealed a putative signal peptide and a mature peptide of 77 amino acids including six cysteine residues. Computer-aided secondary structure analysis predicted that the peptide would be composed of four adjacent alpha-helices, and CD spectroscopy indicated an all alpha-helical conformation. The tertiary structure appears to be stabilized by three disulfide bonds; the pore-forming activity was not sensitive to heat but was lost in the presence of reducing agents. Sequence homology was found to the saposins and to surfactant-associated protein B, both mammalian polypeptides of similar size and secondary structure but of non-lytic function. In particular, the six cysteine residues were found to be conserved, suggesting a common motif for stabilizing a favourable tertiary structure. Compared with previously characterized toxic peptides also containing three disulfide bonds, the amoeba peptide may represent a distinct class of biologically active peptides.
authors.affiliation: Department of Molecular Biology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Leippe
authors.forename: E
authors.initials: E
authors.lastname: Tannich
authors.forename: R
authors.initials: R
authors.lastname: Nickel
authors.forename: G
authors.initials: G
authors.lastname: van der Goot
authors.forename: F
authors.initials: F
authors.lastname: Pattus
authors.forename: R D
authors.initials: RD
authors.lastname: Horstmann
authors.forename: H J
authors.initials: HJ
authors.lastname: Müller-Eberhard
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D002942:Circular Dichroism; D016054:DNA, Protozoan / Q000235:genetics / Q000302:isolation & purification; D004748:Entamoeba histolytica / Q000235:genetics*; D015723:Gene Library; D007473:Ion Channels; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics; D016053:RNA, Protozoan / Q000235:genetics / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
chemical_list: D016054:DNA, Protozoan; D007473:Ion Channels; D008565:Membrane Proteins; D015800:Protozoan Proteins; D016053:RNA, Protozoan; D011994:Recombinant Proteins; C041670:amoebapore proteins, protozoan