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Ectatomin
From Proteopedia
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==Introduction== | ==Introduction== | ||
<StructureSection load='1stp' size='340' side='right' caption='Caption for this structure' scene=''> | <StructureSection load='1stp' size='340' side='right' caption='Caption for this structure' scene=''> | ||
| - | ''Ectatomma tuberculatum'' has one of the most toxic venoms known among ants. A total of 48 proteins have been identified within the venom of these ants. A neurotoxin,<scene name='84/841096/Ectatomin_use_this_one/1'>ectatomin</scene>, is responsible for the major toxic effect of the venom in mammals and insects.<ref> | + | ''Ectatomma tuberculatum'' has one of the most toxic venoms known among ants. A total of 48 proteins have been identified within the venom of these ants. A neurotoxin,<scene name='84/841096/Ectatomin_use_this_one/1'>ectatomin</scene>, is responsible for the major toxic effect of the venom in mammals and insects.<ref>Nolde, D. E., et al. “Three-Dimensional Structure of Ectatomin from Ectatomma Tuberculatum Ant Venom.” Journal Of Biomolecular NMR, vol. 5, no. 1, Jan. 1995, pp. 1–13. EBSCOhost, search.ebscohost.com/login.aspx?direct=true&db=mdc&AN=7881269&site=eds-live&scope=site</ref> |
== Structure == | == Structure == | ||
| - | Ectatomin is a highly basic toxin and contains <scene name='84/841096/Scene_2/1'> two homologous polypeptide chains linked to each other by a disulfide bond.</scene> <scene name='84/841096/Scene_3/3'>The two anti-parallel alpha helical chains consist of 37 and 34 amino acid residues</scene> with an <scene name='84/841096/Disulfide_bridge/1'>internal disulfide bridge</scene> in each chain that forms a hairpin. In aqueous solution ectatomin forms a four-alpha helix bundle. | + | Ectatomin is a highly basic toxin and contains <scene name='84/841096/Scene_2/1'> two homologous polypeptide chains linked to each other by a disulfide bond.</scene> <scene name='84/841096/Scene_3/3'>The two anti-parallel alpha helical chains consist of 37 and 34 amino acid residues</scene> with an <scene name='84/841096/Disulfide_bridge/1'>internal disulfide bridge</scene> in each chain that forms a hairpin. In aqueous solution ectatomin forms a four-alpha helix bundle.<ref>Nolde, D. E., et al. “Three-Dimensional Structure of Ectatomin from Ectatomma Tuberculatum Ant Venom.” Journal Of Biomolecular NMR, vol. 5, no. 1, Jan. 1995, pp. 1–13. EBSCOhost, search.ebscohost.com/login.aspx?direct=true&db=mdc&AN=7881269&site=eds-live&scope=site.</ref> |
== Channel Formation == | == Channel Formation == | ||
Ectatomin has channel-forming activity. It forms nonselective cation channels in membrane systems and the channel formation depends on membrane potentials and occurs only at a positive cis-potential. Each pore is formed by two ectatomin molecules. This channel-forming property of ectatomin may account partially for its toxic activity. The high level of ectatomin’s toxicity implies that there may be specific cellular targets for its action. <ref>Silva, Juliana Rocha da, et al. “Assessing the Proteomic Activity of the Venom of the Ant Ectatomma Tuberculatum (Hymenoptera: Formicidae: Ectatomminae).” Psyche: A Journal of Entomology, June 2018, pp. 1–11. EBSCOhost, doi:10.1155/2018/7915464.</ref> | Ectatomin has channel-forming activity. It forms nonselective cation channels in membrane systems and the channel formation depends on membrane potentials and occurs only at a positive cis-potential. Each pore is formed by two ectatomin molecules. This channel-forming property of ectatomin may account partially for its toxic activity. The high level of ectatomin’s toxicity implies that there may be specific cellular targets for its action. <ref>Silva, Juliana Rocha da, et al. “Assessing the Proteomic Activity of the Venom of the Ant Ectatomma Tuberculatum (Hymenoptera: Formicidae: Ectatomminae).” Psyche: A Journal of Entomology, June 2018, pp. 1–11. EBSCOhost, doi:10.1155/2018/7915464.</ref> | ||
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Ectatomin is inserted effectively and efficiently into the plasma membrane at a concentration of 5 x 10-7 M and does not penetrate through the cell membranes.<ref>Pluzhnikov, K., et al. “Analysis of Ectatomin Action on Cell Membranes.” European Journal Of Biochemistry, vol. 262, no. 2, June 1999, pp. 501–506. EBSCOhost, search.ebscohost.com/login.aspx?direct=true&db=mdc&AN=10336635&site=eds-live&scope=site.</ref> | Ectatomin is inserted effectively and efficiently into the plasma membrane at a concentration of 5 x 10-7 M and does not penetrate through the cell membranes.<ref>Pluzhnikov, K., et al. “Analysis of Ectatomin Action on Cell Membranes.” European Journal Of Biochemistry, vol. 262, no. 2, June 1999, pp. 501–506. EBSCOhost, search.ebscohost.com/login.aspx?direct=true&db=mdc&AN=10336635&site=eds-live&scope=site.</ref> | ||
== Hemolytic and Cytolytic Effects == | == Hemolytic and Cytolytic Effects == | ||
| - | Hemolytic activities of ectatomin were determined in rabbit erythrocytes with 78 HU*mg-1 and 41 HU*mg-1 . The cytolytic activity of ectatomin was observed in Sf9 cells and was (2 +/- 0.8) x 10-6 M. These hemolytic and cytolytic effects are seen at high concentrations (0.5 x 10-6 to 10-5). At these high concentrations, ectatomin damages cell membranes in a detergent-like or pore-forming fashion. This supports that the binding of the ectatomin to cell membranes is nondescriminative; it involves lipids rather than specific receptor molecules. | + | Hemolytic activities of ectatomin were determined in rabbit erythrocytes with 78 HU*mg-1 and 41 HU*mg-1 . The cytolytic activity of ectatomin was observed in Sf9 cells and was (2 +/- 0.8) x 10-6 M. These hemolytic and cytolytic effects are seen at high concentrations (0.5 x 10-6 to 10-5). At these high concentrations, ectatomin damages cell membranes in a detergent-like or pore-forming fashion. This supports that the binding of the ectatomin to cell membranes is nondescriminative; it involves lipids rather than specific receptor molecules.<ref>Pluzhnikov, K., et al. “Analysis of Ectatomin Action on Cell Membranes.” European Journal Of Biochemistry, vol. 262, no. 2, June 1999, pp. 501–506. EBSCOhost, search.ebscohost.com/login.aspx?direct=true&db=mdc&AN=10336635&site=eds-live&scope=site.</ref> |
==Effect on Cardiac Ca2+ Channels == | ==Effect on Cardiac Ca2+ Channels == | ||
| - | Ectatomin has inhibitory effects on cardiac Ca2+ channels. These inhibitory effects occur at concentrations of 10-11 to 10-8 M. The inhibitions at specific concentrations suggest that there is a specific receptor, which could possibly be the Ca2+ channels. Ectatomin modulates the activity of calcium channels and blocks calcium channels. Although it is not only limited to the blockage of the calcium channels. It is also possible that ectatomin interacts directly or allosterically with β-adrenergic receptors in their agonist-occupied state. The mechanism is not clear, but this interaction may limit the receptor to transition to its agonist-free state. | + | Ectatomin has inhibitory effects on cardiac Ca2+ channels. These inhibitory effects occur at concentrations of 10-11 to 10-8 M. The inhibitions at specific concentrations suggest that there is a specific receptor, which could possibly be the Ca2+ channels. Ectatomin modulates the activity of calcium channels and blocks calcium channels. Although it is not only limited to the blockage of the calcium channels. It is also possible that ectatomin interacts directly or allosterically with β-adrenergic receptors in their agonist-occupied state. The mechanism is not clear, but this interaction may limit the receptor to transition to its agonist-free state.<ref>Pluzhnikov, K., et al. “Analysis of Ectatomin Action on Cell Membranes.” European Journal Of Biochemistry, vol. 262, no. 2, June 1999, pp. 501–506. EBSCOhost, search.ebscohost.com/login.aspx?direct=true&db=mdc&AN=10336635&site=eds-live&scope=site.</ref> |
==Inhibiting Autophosphorylation == | ==Inhibiting Autophosphorylation == | ||
| - | Ectatomin has inhibitory effects on autophosphorylation in calcium channels. There are at least two distinct phosphorylation sites that are known for the channels. The inhibition of both phosphorylation sites has the same effect on the calcium channels. The inhibition causes the channels to stay open and the become nonspecific. Ions may flow freely. | + | Ectatomin has inhibitory effects on autophosphorylation in calcium channels. There are at least two distinct phosphorylation sites that are known for the channels. The inhibition of both phosphorylation sites has the same effect on the calcium channels. The inhibition causes the channels to stay open and the become nonspecific. Ions may flow freely.<ref> Pluzhinikov KA, Nol'de DE, Tertyshnikova SM, et al. [Structure-activity study of the basic toxic component of venom from the ant Ectatomma tuberculatum] Bioorganicheskaia Khimiia. 1994 Aug-Sep;20(8-9):857-871.</ref> |
==Additional Resources == | ==Additional Resources == | ||
[https://www.youtube.com/watch?v=XOHGdPdCYHs Proposed mechanism for pore formation] | [https://www.youtube.com/watch?v=XOHGdPdCYHs Proposed mechanism for pore formation] | ||
== References == | == References == | ||
<references/> | <references/> | ||
| - | Nolde, D. E., et al. “Three-Dimensional Structure of Ectatomin from Ectatomma Tuberculatum Ant Venom.” Journal Of Biomolecular NMR, vol. 5, no. 1, Jan. 1995, pp. 1–13. EBSCOhost, search.ebscohost.com/login.aspx?direct=true&db=mdc&AN=7881269&site=eds-live&scope=site. | ||
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| - | Pluzhnikov, K., et al. “Analysis of Ectatomin Action on Cell Membranes.” European Journal Of Biochemistry, vol. 262, no. 2, June 1999, pp. 501–506. EBSCOhost, search.ebscohost.com/login.aspx?direct=true&db=mdc&AN=10336635&site=eds-live&scope=site. | ||
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| - | Pluzhinikov KA, Nol'de DE, Tertyshnikova SM, et al. [Structure-activity study of the basic toxic component of venom from the ant Ectatomma tuberculatum] Bioorganicheskaia Khimiia. 1994 Aug-Sep;20(8-9):857-871. | ||
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| - | Silva, Juliana Rocha da, et al. “Assessing the Proteomic Activity of the Venom of the Ant Ectatomma Tuberculatum (Hymenoptera: Formicidae: Ectatomminae).” Psyche: A Journal of Entomology, June 2018, pp. 1–11. EBSCOhost, doi:10.1155/2018/7915464. | ||
Revision as of 03:11, 29 April 2020
Introduction
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