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-Aminobutyric Acid Increases the Water Accessibility of M3 Membrane-Spanning Segment Residues in -Aminobutyric Acid Type A Receptors

Summary: -Aminobutyric Acid Increases the Water Accessibility of M3 Membrane-
Spanning Segment Residues in -Aminobutyric Acid Type A Receptors
Daniel B. Williams*#
and Myles H. Akabas*
*Center for Molecular Recognition, #
Integrated Program in Cellular, Molecular, and Biophysical Studies, and
Department of Physiology
and Cellular Biophysics and Department of Medicine, College of Physicians and Surgeons, Columbia University, New York,
New York 10032 USA
ABSTRACT -Aminobutyric acid type A (GABAA) receptors are members of the ligand-gated ion channel gene superfamily.
Using the substituted cysteine accessibility method, we investigated whether residues in the 1M3 membrane-spanning
segment are water-accessible. Cysteine was substituted, one at a time, for each M3 residue from 1Ala291
to 1Val307
. The
ability of these mutants to react with the water-soluble, sulfhydryl-specific reagent pCMBS was assayed electrophysiologi-
cally. Cysteines substituted for 1Ala291
and 1Tyr294
reacted with pCMBS applied both in the presence and in the absence
of GABA. Cysteines substituted for 1Phe298
, 1Ala300


Source: Akabas, Myles - Department of Physiology and Biophysics, Albert Einstein College of Medicine, Yeshiva University


Collections: Biology and Medicine