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Ion selectivity and membrane potential effects of two scorpion pore-forming peptides

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dc.contributor.advisor Du Plessis JL, Mr en
dc.contributor.advisor Verdonck F, Prof en
dc.contributor.author Elgar D en
dc.date.accessioned 2016-09-22T07:19:27Z
dc.date.available 2016-09-22T07:19:27Z
dc.date.submitted 2005 en
dc.identifier.uri http://hdl.handle.net/20.500.11892/14260
dc.description.abstract Parabutoporin (PP) and opistoporin 1 (OP1) are cation, &alpha;-helical antimicrobial peptides isolated from the southern African scorpion species, Parabuthus schlechteri and Opistophthalmus carinatus, respectively. Along with their antimicrobial action against bacteria and fungi, these peptides show pore-forming properties in the membranes of mammalian cells. Pore-formation and ion selectivity in cardiac myocytes were investigated by measuring the whole cell leak current by means of the patch clamp technique. Pore-formation was observed as the induction of leak currents. Ion selectivity of the pores was indicated by the shift of the reversal potential (E<sub>rev</sub>) upon substitution of intra (K<sup>+</sup> with Cs<sup>+</sup> and CI<sup>-</sup> with aspartate) and extracellular (Na<sup>+</sup> with NMDG<sup>+</sup>) ions. Results were compared with the effect of gramicidin A used as a positive control for monovalent cation selective pores. PP and OP1 induced a fluctuating leak current and indicate non-selectivity of PP and OP 1-induced pores. An osmotic protection assay to determine estimated pore size was performed on the cardiac myocytes. PP and OP 1-induced pores had an estimate pore size of 1.38-1.78 nm in diameter.<br><br> The effect of PP and OP1 on the membrane potential (MP) of a neuroblastoma cell line and cardiac myocytes was investigated. TMRM was used to mark the MP fluorescently and a confocal microscope used to record the data digitally. The resting membrane potential (RMP) of the neuroblastoma cells was calculated at -38.3 &plusmn; 1.9 mV. PP (0.5 &mu;M) and OP1 (0.5-1 &mu;M) depolarized the entire cell uniformly to a MP of-11.9 &plusmn; 3.9 mV and -9.4 &plusmn;1.9 mV, respectively. This occurred after 20-30 min of peptide exposure. In the case of the cardiac myocytes depolarization was induced to -39.7 &plusmn; 8.4 mV and -32.6 &plusmn; 5.2 mV by 0.5-1 &mu;M PP and 1.5-2.5 &mu;M OP1, respectively. en
dc.language English en
dc.subject Medical sciences: Physiology en
dc.subject Biophysics, medical biochemistry, control processes, tissue and organ culture en
dc.title Ion selectivity and membrane potential effects of two scorpion pore-forming peptides en
dc.type Masters degree en
dc.description.degree MSc en

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