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Surface charge potentiates conduction through the cardiac ryanodine receptor channel
Q Tu1, P Velez, M Cortes-Gutierrez
1Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston 77555-0641.
The Journal of General Physiology
|May 1, 1994
Summary
Negative surface charge near cardiac calcium release channels enhances ion flow. This charge acts as a filter, potentially increasing local calcium concentrations for better channel function.
Area of Science:
- Biophysics
- Cardiovascular Physiology
- Ion Channel Function
Background:
- Cardiac sarcoplasmic reticulum (SR) Ca2+ release channels are crucial for muscle contraction.
- Understanding factors influencing channel conductance is vital for cardiac health.
Purpose of the Study:
- To investigate the role of surface charge in cardiac SR Ca2+ release channel currents.
- To determine if surface charge affects ion conduction and selectivity.
Main Methods:
- Single channel currents were measured using barium (Ba2+) and cesium (Cs+) as charge carriers.
- Ionic strength and surface charge density were manipulated.
- Channel identity and sidedness were confirmed pharmacologically.
Main Results:
- Asymmetric Cs+ conduction (lumenal to myoplasmic direction greater than reverse) was observed at low ionic strength.
- Conduction saturated at high ionic strength, indicating a change in ion interaction.
- Neutralizing lumenal carboxyl groups significantly reduced channel conduction.
Conclusions:
- Negative surface charge is present near the lumenal mouth of cardiac SR Ca2+ release channels.
- This surface charge potentiates ion conduction by increasing local Ca2+ concentration.
- The surface charge acts as a preselection filter for the channel.