Interaction of alkanols and local anesthetics with spin-labeled Ca2+-ATPase of sarcoplasmic reticulum vesicles

AbstractAlkanols and tertiary amine herivative local anesthetics modify the activity of Ca2+-ATPase. In orher to investigate the primary binding sites, associated to the functional changes, sarcoplasmic reticulum (SR) Ca2+-ATPase was labeled with maleimive herivative spin labels which bind covalently to SH groups of cysteine residues and allow to probe the regions of the protein close to those residues. The EPR measurements showed motional constraints induced by drug-treatment which indicate changes in the enzyme dynamics and structure. n-Alkanols are shown to affect some of the protein-bound labels by restricting their motion. There is, however, no correlation between the functional effects and the observed motional restriction, in the sense that concentrations of the different alcohols leading to the same functional effects do not induce the same vegree of restriction. Dibucaine and tetracaine at functional relehant concentrations also restrict the movement of protein bound labels. But, in this case, correlation between spectral changes and functional effects is observed