title: Primary structure of echotoxin 2, an actinoporin-like hemolytic toxin from the salivary gland of the marine gastropod Monoplex echo.
abstract: Echotoxins are 25 kDa proteins with both hemolytic and lethal activities, previously purified from the salivary gland of the marine gastropod Monoplex echo. In this study, a cDNA encoding echotoxin 2 was cloned by RT-PCR, 3'-RACE and 5'-RACE, based on its partial amino acid sequence. The full-length echotoxin 2 cDNA (1000 bp) obtained contains an open reading frame (825 bp) coding for a precursor protein of 274 amino acid residues. Mature echotoxin 2 composed of 226 amino acid residues is assumed to be produced by post-translational removal of N-terminal 23 residues (predicted as a signal peptide) and C-terminal 25 residues from the precursor protein. Very interestingly, a homology search revealed that echotoxin 2 is analogous to actinoporins, 20 kDa pore-forming hemolysins reported from various sea anemones. In addition to the similarities in biological activity, molecular size and basicity between echotoxin 2 and actinoporins, two prominent structural features, an N-terminal amphiphilic alpha-helix and an aromatic patch comprising Trp and Tyr residues, both of which are important for the pore-forming activity of actinoporins, are also recognized in echotoxin 2. However, echotoxin 2 is distinguishable from actinoporins in having Cys residues and lacking an RGD motif.
authors.affiliation: Department of Food Science and Technology, Tokyo University of Fisheries, Konan-4, Minato-ku, Tokyo 108-8477, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Kawashima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nagai
authors.forename: Masami
authors.initials: M
authors.lastname: Ishida
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nagashima
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shiomi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003545:Cysteine / Q000378:metabolism; D006460:Hemolysin Proteins / Q000737:chemistry / Q000378:metabolism*; D008387:Marine Toxins / Q000737:chemistry* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D008970:Molecular Weight; D008974:Mollusca / Q000737:chemistry*; D021382:Protein Sorting Signals; D017433:Protein Structure, Secondary; D012469:Salivary Glands / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid
chemical_list: D006460:Hemolysin Proteins; D008387:Marine Toxins; D021382:Protein Sorting Signals; D003545:Cysteine