Comparison of CHAPS-Induced Current Fluctuations with Sarcoplasmic Reticulum Ca²⁺ Release Channel Activity

Abstract

The process of purifying and reconstituting transport membrane proteins generally involves the use of detergents, which often cannot be completely separated from the proteins. The effects of the zwitterionic detergent CHAPS on planar lipid bilayers have been measured, and it is demonstrated that CHAPS can induce microscopic electrical activity in the bilayers. Typical CHAPS-induced activity consists of large current bursts, often separated by intervals of quiescent activity, with no definable conductance levels. The size of the current bursts is generally increased by higher CHAPS concentration or by millimolar ATP and usually reduced by millimolar Mg²⁺ and micromolar ruthenium red. The response of the CHAPS-induced currents to these agents is compared to that of the ligand-gated Ca²⁺ release channel of muscle sarcoplasmic reticulum.

Key Words:

• CHAPS
• detergents
• planar lipid bilayers
• electrical conductivity