A model membrane protein for binding volatile anesthetics.
Earlier work demonstrated that a water-soluble four-helix bundle protein designed with a cavity in its nonpolar core is capable of binding the volatile anesthetic halothane with near-physiological affinity (0.7 mM Kd). To create a more relevant, model membrane protein receptor for studying the physicochemical specificity of anesthetic binding, we have synthesized a new protein that builds on the anesthetic-binding, hydrophilic four-helix bundle and incorporates a hydrophobic domain capable of ion-channel activity, resulting in an amphiphilic four-helix bundle that forms stable monolayers at the air/water interface. The affinity of the cavity within the core of the bundle for volatile anesthetic binding is decreased by a factor of 4-3.1 mM Kd as compared to its water-soluble counterpart. Nevertheless, the absence of the cavity within the otherwise identical amphiphilic peptide significantly decreases its affinity for halothane similar to its water-soluble counterpart. Specular x-ray reflectivity shows that the amphiphilic protein orients vectorially in Langmuir monolayers at higher surface pressure with its long axis perpendicular to the interface, and that it possesses a length consistent with its design. This provides a successful starting template for probing the nature of the anesthetic-peptide interaction, as well as a potential model system in structure/function correlation for understanding the anesthetic binding mechanism.
Department of Chemistry, Department of Anesthesiology, University of Pennsylvania, Philadelphia, Pennsylvania.
Shixin
S
Ye
Joseph
J
Strzalka
Inna Y
IY
Churbanova
Songyan
S
Zheng
Jonas S
JS
Johansson
J Kent
JK
Blasie
D000595:Amino Acid Sequence; D018685:Anesthetics, Inhalation / Q000737:chemistry; D001665:Binding Sites; D015195:Drug Design; D006221:Halothane / Q000737:chemistry*; D007473:Ion Channels / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012995:Solubility
D018685:Anesthetics, Inhalation; D007473:Ion Channels; D008565:Membrane Proteins; D006221:Halothane