Identification of anesthetic binding sites on human serum albumin using a novel etomidate photolabel.

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Bright DP, Adham SD, Lemaire LC, Benavides R, Gruss M, Taylor GW, Smith EH, Franks NP

Identification of anesthetic binding sites on human serum albumin using a novel etomidate photolabel.

J Biol Chem. 2007 Apr 20;282(16):12038-47. Epub 2007 Feb 20.

PubMed ID

17311911 [ View in PubMed

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Abstract

We have synthesized a novel analog of the general anesthetic etomidate in which the ethoxy group has been replaced by an azide group, and which can be used as a photolabel to identify etomidate binding sites. This acyl azide analog is a potent general anesthetic in both rats and tadpoles and, as with etomidate, is stereoselective in its actions, with the R(+) enantiomer being significantly more potent than the S(-) enantiomer. Its effects on alpha1beta2gamma2s GABA(A) receptors expressed in HEK-293 cells are virtually indistinguishable from the parent compound etomidate, showing stereoselective potentiation of GABA-induced currents, as well as direct mimetic effects at higher concentrations. In addition, a point mutation (beta2 N265M), which is known to attenuate the potentiating actions of etomidate, also blocks the effects of the acyl azide analog. We have investigated the utility of the analog to identify etomidate binding sites by using it to photolabel human serum albumin, a protein that binds approximately 75% of etomidate in human plasma and which is thought to play a major role in its pharmacokinetics. Using HPLC/mass spectrometry we have identified two anesthetic binding sites on HSA. One site is the well-characterized drug binding site I, located in HSA subdomain IIA, and the second site is also an established drug binding site located in subdomain IIIB, which also binds propofol. The acyl azide etomidate may prove to be a useful new photolabel to identify anesthetic binding sites on the GABA(A) receptor or other putative targets.

DrugBank Data that Cites this Article

Drug Carriers

Drug	Carrier	Kind	Organism	Pharmacological Action	Actions
Propofol	Serum albumin	Protein	Humans	No	Not Available	Details

Binding Properties

Drug	Target	Property	Measurement	pH	Temperature (°C)
Etomidate	Gamma-aminobutyric acid receptor subunit alpha-1	EC 50 (nM)	11000	N/A	N/A	Details