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 sk eletal muscle fibres is modified by halothane and because protein-protein i nteractions play an important role in the regulation of Ca2+-regulatory pro teins, we investigated the effect of this volatile drug on the oligomerizat ion of the fast-twitch Ca2+-ATPase. Using electrophoretic separation follow ing incubation with halothane, increases in relative molecular mass were de termined by immunoblotting with a monoclonal antibody to the SERCA1 isoform of the Ca2+-ATPase. Distinct drug-induced decreases in electrophoretic mob ility indicated oligomerization of the native Ca2+-pump by halothane, compa rable to crosslinking-mediated formation of homo-tetramers. Determination o f the effect of halothane on enzyme activity suggested that halothane-media ted protein aggregation triggers a partial inhibition of Ca2+-pump units. T hus, halothane appears to exert its action via specific peptide binding sit es and not indirectly by lipid perturbation These findings support the prot ein theory of anesthetic action. (C) 2000 Academic Press.