![]() |
|
|
Departments of Physiology and Biophysics and of Neuroscience, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York
The GABAA receptor is a target of many general anesthetics. The low affinity of general anesthetics has complicated the search for the location of anesthetic binding sites. Attention has focused on two pairs of residues near the extracellular ends of the M2 and M3 membrane-spanning segments,
1Ser270/
2Asn265 (15'M2) and
1Ala291/
2Met286 (M3). In the 4-Å resolution acetylcholine receptor structure, the aligned positions are separated by
10 Å. To determine whether these residues are part of a binding site for propofol, an intravenous anesthetic, we probed propofol's ability to protect cysteines substituted for these residues from modification by the sulfhydryl-specific reagentp-chloromercuribenzenesulfonate (pCMBS-). pCMBS- reacted with cysteines substituted at the four positions in the absence and presence of GABA. Because propofol binding induces conformational change in the GABAAreceptor, we needed to establish a reference state of the receptor to compare reaction rates in the absence and presence of propofol. We compared reaction rates in the presence of GABA with those in the presence of propofol +GABA. The GABA concentration was reduced to give a similar fraction of the maximal GABA current in both conditions. Propofol protected, in a concentration-dependent manner, the cysteine substituted for
2Met286 from reaction with pCMBS-. Propofol did not protect the cysteine substituted for the aligned
1 subunit position or the 15'M2 segment Cys mutants in either subunit. We infer that propofol may bind near the extracellular end of the
subunit M3 segment.
Address correspondence to: Dr. Myles Akabas, Department of Physiology and Biophysics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461. E-mail: makabas{at}aecom.yu.edu
This article has been cited by other articles:
![]() |
C. Lynch III Meyer and Overton Revisited Anesth. Analg., September 1, 2008; 107(3): 864 - 867. [Full Text] [PDF] |
||||
![]() |
J. Mercado and C. Czajkowski {gamma}-Aminobutyric Acid (GABA) and Pentobarbital Induce Different Conformational Rearrangements in the GABAA Receptor {alpha}1 and {beta}2 Pre-M1 Regions J. Biol. Chem., May 30, 2008; 283(22): 15250 - 15257. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Rosen, M. Bali, J. Horenstein, and M. H. Akabas Channel Opening by Anesthetics and GABA Induces Similar Changes in the GABAA Receptor M2 Segment Biophys. J., May 1, 2007; 92(9): 3130 - 3139. [Abstract] [Full Text] [PDF] |
||||
![]() |
G.-D. Li, D. C. Chiara, G. W. Sawyer, S. S. Husain, R. W. Olsen, and J. B. Cohen Identification of a GABAA Receptor Anesthetic Binding Site at Subunit Interfaces by Photolabeling with an Etomidate Analog. J. Neurosci., November 8, 2006; 26(45): 11599 - 11605. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Jansen and M. H. Akabas State-dependent cross-linking of the M2 and M3 segments: functional basis for the alignment of GABAA and acetylcholine receptor M3 segments. J. Neurosci., April 26, 2006; 26(17): 4492 - 4499. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Ernst, S. Bruckner, S. Boresch, and W. Sieghart Comparative Models of GABAA Receptor Extracellular and Transmembrane Domains: Important Insights in Pharmacology and Function Mol. Pharmacol., November 1, 2005; 68(5): 1291 - 1300. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. J. Law, R. H. Henchman, and J. A. McCammon Chemical Theory and Computation Special Feature: A gating mechanism proposed from a simulation of a human {alpha}7 nicotinic acetylcholine receptor PNAS, May 10, 2005; 102(19): 6813 - 6818. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. Arevalo, D. C. Chiara, S. A. Forman, J. B. Cohen, and K. W. Miller Gating-enhanced Accessibility of Hydrophobic Sites within the Transmembrane Region of the Nicotinic Acetylcholine Receptor's {delta}-Subunit: A TIME-RESOLVED PHOTOLABELING STUDY J. Biol. Chem., April 8, 2005; 280(14): 13631 - 13640. [Abstract] [Full Text] [PDF] |
||||
![]() |
I. T. Awad and V. Chan Developing yet another spinal analgesic drug?/Encore un autre analgesique rachidien ? Can J Anesth, November 1, 2004; 51(9): 871 - 874. [Full Text] [PDF] |
||||
![]() |
I. A. Lobo, M. P. Mascia, J. R. Trudell, and R. A. Harris Channel Gating of the Glycine Receptor Changes Accessibility to Residues Implicated in Receptor Potentiation by Alcohols and Anesthetics J. Biol. Chem., August 6, 2004; 279(32): 33919 - 33927. [Abstract] [Full Text] [PDF] |
||||