Inactivation of the calcium-transport ATPase in the sarcoplasmic reticulum by the combined effect of lasolocid and Triton X-100.

The calcium-transport ATPase of the sarcoplasmic reticulum membranes is irreversibly inactivated by the combined action of Lasolocid and Triton X-100 at concentrations which separately do not interfere with the enzyme's activity. In the presence of Lasolocid the enzyme is most susceptible to inactivation when the Triton X-100 concentration just exceeds its critical micellar concentration, approximately, 0.2 mg X ml-1. Lasolocid becomes effective at a concentration of 10 microM and produces rapid inactivation at 100 microM. Phosphoprotein formation is less affected than phosphate liberation. The influence of the ATPase protein on the fluorescence intensity of Lasolocid passes a distinct maximum at the most effective Triton X-100 concentration of 0.2 mg X ml-1.