title: δ/ω-Plectoxin-Pt1a: an excitatory spider toxin with actions on both Ca(2+) and Na(+) channels.
abstract: The venom of spider Plectreurys tristis contains a variety of peptide toxins that selectively target neuronal ion channels. O-palmitoylation of a threonine or serine residue, along with a characteristic and highly constrained disulfide bond structure, are hallmarks of a family of toxins found in this venom. Here, we report the isolation and characterization of a new toxin, δ/ω-plectoxin-Pt1a, from this spider venom. It is a 40 amino acid peptide containing an O-palmitoylated Ser-39. Analysis of δ/ω-plectoxin-Pt1a cDNA reveals a small precursor containing a secretion signal sequence, a 14 amino acid N-terminal propeptide, and a C-terminal amidation signal. The biological activity of δ/ω-plectoxin-Pt1a is also unique. It preferentially blocks a subset of Ca(2+) channels that is apparently not required for neurotransmitter release; decreases threshold for Na(+) channel activation; and slows Na(+) channel inactivation. As δ/ω-plectoxin-Pt1a enhances synaptic transmission by prolonging presynaptic release of neurotransmitter, its effects on Na(+) and Ca(2+) channels may act synergistically to sustain the terminal excitability.
authors.affiliation: Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida, USA. yzhou@fsu.edu
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhou
authors.forename: Mingli
authors.initials: M
authors.lastname: Zhao
authors.forename: Gregg B
authors.initials: GB
authors.lastname: Fields
authors.forename: Chun-Fang
authors.initials: CF
authors.lastname: Wu
authors.forename: W Dale
authors.initials: WD
authors.lastname: Branton
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002121:Calcium Channel Blockers / Q000737:chemistry / Q000633:toxicity*; D015220:Calcium Channels / Q000378:metabolism*; D004330:Drosophila / Q000166:cytology; D054878:Lipoylation; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009498:Neurotoxins / Q000737:chemistry / Q000235:genetics / Q000633:toxicity*; D026941:Sodium Channel Blockers / Q000737:chemistry / Q000633:toxicity*; D015222:Sodium Channels / Q000378:metabolism*; D013111:Spider Venoms / Q000737:chemistry*
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D009498:Neurotoxins; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013111:Spider Venoms