Effect of halothane on the oligomerization of the sarcoplasmic reticulum Ca2+-ATPase

The exact molecular mechanism of inhalational anesthetics remains obscure. Since the enzyme activity of the sarcoplasmic reticulum Ca2+-ATPase from skeletal muscle fibres is modified by halothane and because protein-protein interactions play an important role in the regulation of Ca2+-regulatory proteins, we investigated the effect of this volatile drug on the oligomerization of the fast-twitch Ca2+-ATPase. Using electrophoretic separation following incubation with halothane, increases in relative molecular mass were determined by immunoblotting with a monoclonal antibody to the SERCA1 isoform of the Ca2+-ATPase. Distinct drug-induced decreases in electrophoretic mobility indicated oligomerization of the native Ca2+-pump by halothane, comparable to crosslinking-mediated formation of homo-tetramers. Determination of the effect of halothane on enzyme activity suggested that halothane-mediated protein aggregation triggers a partial inhibition of Ca2+-pump units. Thus, halothane appears to exert its action via specific peptide binding sites and not indirectly by lipid perturbation These findings support the protein theory of anesthetic action. (C) 2000 Academic Press.