Halothane binds to druggable sites in the [Ca2+]4-calmodulin (CaM) complex, but does not inhibit [Ca2+]4-CaM activation of kinase

Abstract

The mechanism(s) of volatile anesthetics (VA) are poorly understood. We used high resolution NMR spectroscopy to determine the structure of the halothane/calmodulin([Ca2+]4-CaM) complex, and found that halothane molecules bind in the druggable sites. We then examined whether VA binding to druggable sites in calmodulin would effect [Ca2+]4-CaM dependent activity of myosin light chain kinase. We used fluorescence assays to determine that VA effect [Ca2+]4-CaM activation of smooth-muscle-myosin-light-chain-kinase (smMLCK), but not the Kd of [Ca2+]4-CaM binding to skeletal-myosin-light-chain-kinase-peptide recognition sequence (skMLCKp). These results suggest that VA do not alter [Ca2+]4-CaM dependent MLCK activity via direct interactions with [Ca2+]4-CaM.