Lipid surface charge does not influence conductance or calcium block of single sodium channels in planar bilayers
| Autor: | B.A. Pailthorpe, Robert J. French, J.F. Worley rd, Bruce K. Krueger |
|---|---|
| Rok vydání: | 1992 |
| Předmět: |
Membrane lipids
Lipid Bilayers Analytical chemistry Synthetic membrane Phospholipid Biophysics In Vitro Techniques Models Biological Biophysical Phenomena Sodium Channels Divalent Membrane Lipids chemistry.chemical_compound Electrochemistry Animals Surface charge chemistry.chemical_classification Osmolar Concentration Electric Conductivity Brain Conductance Rats Membrane chemistry Ionic strength Calcium Research Article |
| Zdroj: | Biophysical Journal. 61(5):1353-1363 |
| ISSN: | 0006-3495 |
| DOI: | 10.1016/s0006-3495(92)81942-2 |
| Popis: | We have studied the effects of membrane surface charge on Na+ ion permeation and Ca2+ block in single, batrachotoxin-activated Na channels from rat brain, incorporated into planar lipid bilayers. In phospholipid membranes with no net charge (phosphatidylethanolamine, PE), at low divalent cation concentrations (approximately 100 microM Mg2+), the single channel current-voltage relation was linear and the single channel conductance saturated with increasing [Na+] and ionic strength, reaching a maximum (gamma max) of 31.8 pS, with an apparent dissociation constant (K0.5) of 40.5 mM. The data could be approximated by a rectangular hyperbola. In negatively charged bilayers (70% phosphatidylserine, PS; 30% PE) slightly larger conductances were observed at each concentration, but the hyperbolic form of the conductance-concentration relation was retained (gamma max = 32.9 pS and K0.5 = 31.5 mM) without any preferential increase in conductance at lower ionic strengths. Symmetrical application of Ca2+ caused a voltage-dependent block of the single channel current, with the block being greater at negative potentials. For any given voltage and [Na+] this block was identical in neutral and negatively charged membranes. These observations suggest that both the conduction pathway and the site(s) of Ca2+ block of the rat brain Na channel protein are electrostatically isolated from the negatively charged headgroups on the membrane lipids. |
| Databáze: | OpenAIRE |
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