| Autor: |
Mikov AN; Department of Molecular Neurobiology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Russia., Fedorova IM; Laboratory of Biophysics of Synaptic Processes, I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry RAS, Russia., Potapieva NN; Laboratory of Biophysics of Synaptic Processes, I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry RAS, Russia., Maleeva EE; Department of Molecular Neurobiology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Russia., Andreev YA; Department of Molecular Neurobiology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Russia., Zaitsev AV; Laboratory of Biophysics of Synaptic Processes, I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry RAS, Russia., Kim KK; Laboratory of Biophysics of Synaptic Processes, I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry RAS, Russia., Bocharov EV; Department of Structural Biology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Russia.; NBIC Centre, NRC 'Kurchatov Institute', Russia., Bozin TN; NBIC Centre, NRC 'Kurchatov Institute', Russia., Altukhov DA; NBIC Centre, NRC 'Kurchatov Institute', Russia., Lipkin AV; NBIC Centre, NRC 'Kurchatov Institute', Russia., Kozlov SA; Department of Molecular Neurobiology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Russia., Tikhonov DB; Laboratory of Biophysics of Synaptic Processes, I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry RAS, Russia., Grishin EV; Department of Molecular Neurobiology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Russia. |
| Abstrakt: |
Novel disulfide-containing polypeptide toxin was discovered in the venom of the Tibellus oblongus spider. We report on isolation, spatial structure determination and electrophysiological characterization of this 41-residue toxin, called ω-Tbo-IT1. It has an insect-toxic effect with LD50 19 μg/g in experiments on house fly Musca domestica larvae and with LD50 20 μg/g on juvenile Gromphadorhina portentosa cockroaches. Electrophysiological experiments revealed a reversible inhibition of evoked excitatory postsynaptic currents in blow fly Calliphora vicina neuromuscular junctions, while parameters of spontaneous ones were not affected. The inhibition was concentration dependent, with IC50 value 40 ± 10 nM and Hill coefficient 3.4 ± 0.3. The toxin did not affect frog neuromuscular junctions or glutamatergic and GABAergic transmission in rat brains. Ca(2+) currents in Calliphora vicina muscle were not inhibited, whereas in Periplaneta americana cockroach neurons at least one type of voltage gated Ca(2+) current was inhibited by ω-Tbo-IT1. Thus, the toxin apparently acts as an inhibitor of presynaptic insect Ca(2+) channels. Spatial structure analysis of the recombinant ω-Tbo-IT1 by NMR spectroscopy in aqueous solution revealed that the toxin comprises the conventional ICK fold containing an extended β-hairpin loop and short β-hairpin loop which are capable of making "scissors-like mutual motions". |
