Topic
Ectatomin
About: Ectatomin is a research topic. Over the lifetime, 4 publications have been published within this topic receiving 416 citations. The topic is also known as: IPR009458 & Ectatomin.
Papers
TL;DR: The most prominent effect of ectatomin was observed after stimulation of ICa by isoproterenol, an agonist of beta-adrenoreceptors, or forskolin, a stimulator of adenylate cyclase.
Abstract: Ectatomin (m = 7928 Da) is a toxic component from the Ectatomma tuberculatum ant venom containing two homologous polypeptide chains (37 and 34 residues) linked to each other by a disulfide bond. In aqueous solution it forms a four alpha-helix bundle. At concentrations of 0.05-0.1 microm, ectatomin forms channels in cellular and artificial bilayer membranes. Immunochemical analysis of the intracellular distribution of ectatomin showed that the toxin gets efficiently inserted into the plasma membrane at a concentration of 5 x 10-7 m and does not penetrate inside the cell. The effect of ectatomin on cardiac L-type calcium current was studied. Calcium currents (ICa) in isolated rat cardiac ventricular myocytes were measured using the whole-cell perforated patch-clamp technique. It was shown that ectatomin at concentrations of 0.01-10 nm inhibited ICa after a latency of few seconds. ICa was decreased twofold by 10 nm ectatomin. However, the most prominent effect of ectatomin was observed after stimulation of ICa by isoproterenol, an agonist of beta-adrenoreceptors, or forskolin, a stimulator of adenylate cyclase. At a concentration of 1 nm, ectatomin abolished the isoproterenol- and forskolin-sensitive components of ICa. The inhibitory effect of ectatomin was partially reversed by subsequent application of 2 microm of forskolin, whereas subsequent isoproterenol application did not produce the same effect.
40 citations
TL;DR: The results suggest that the ‘inside‐out’ mechanism of pore formation requires a significant movement of Ea helical parts, which might well explain the toxic activity of EA and at the same time its intracellular activities.
TL;DR: Two-dimensional 1H NMR techniques were used to determine the spatial structure of ectatomin, a toxin from the venom of the ant Ectatomma tuberculatum, and structures were refined by unrestrained energy minimization using the CHARMm program.
Abstract: Two-dimensional 1H NMR techniques were used to determine the spatial structure of ectatomin, a toxin from the venom of the ant Ectatomma tuberculatum. Nearly complete proton resonance assignments for two chains of ectatomin (37 and 34 amino acid residues, respectively) were obtained using 2D TOCSY, DQF-COSY and NOESY experiments. The cross-peak volumes in NOESY spectra were used to define the local structure of the protein and generate accurate proton-proton distance constraints employing the MARDIGRAS program. Disulfide bonds were located by analyzing the global fold of ectatomin, calculated with the distance geometry program DIANA. These data, combined with data on the rate of exchange of amide protons with deuterium, were used to obtain a final set of 20 structures by DIANA. These structures were refined by unrestrained energy minimization using the CHARMm program. The resulting rms deviations over 20 structures (excluding the mobile N- and c-termini of each chain) are 0.75 A for backbone heavy atoms, and 1.25 A for all heavy atoms. The conformations of the two chains are similar. Each chain consists of two alpha-helices and a hinge region of four residues; this forms a hairpin structure which is stabilized by disulfide bridges. The hinge regions of the two chains are connected together by a third disulfide bridge. Thus, ectatomin forms a four-alpha-helical bundle structure.
Journal Article•
TL;DR: A toxic principle of the Ectatomma tuberculatum ant venom called ectatomin was isolated and the channel is dimeric and the mechanism of its formation can be explained in terms of the spatial structure established.
Abstract: A toxic principle of the Ectatomma tuberculatum ant venom called ectatomin was isolated. Ectatomin is a protein with molecular weight 7928 Da. Its complete amino acid sequence and spatial structure in aqueous solution were determined by protein chemistry methods and NMR spectroscopy techniques. Ectatomin contains two highly homologous polypeptide chains linked to each other by a disulfide bond. The chains consist of 37 and 34 amino acid residues with an internal disulfide bridge in each. In aqueous solution the molecule forms a bundle of four amphipathic alpha-helices. This toxin in a concentration of 0.05-0.01 mM forms potential dependent nonselective cation channels both in cell and artificial membranes. The channel is dimeric and the mechanism of its formation can be explained in terms of the spatial structure established.
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 1999 | 1 |
| 1995 | 1 |
| 1994 | 2 |