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Design, synthesis and functional characterization of a pentameric channel protein that mimics the presumed pore structure of the nicotinic cholinergic receptor
Author(s) -
Montal Myrta Oblatt,
Iwamoto Takeo,
Tomich John M.,
Montal Mauricio
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)80599-p
Subject(s) - torpedo , acetylcholine receptor , chemistry , cys loop receptors , nicotinic acetylcholine receptor , ion channel , helix bundle , crystallography , protein subunit , biophysics , nicotinic agonist , receptor , helix (gastropod) , cholinergic , conductance , stereochemistry , protein structure , biochemistry , biology , ecology , mathematics , combinatorics , neuroscience , snail , gene
Nicotinic cholinergic receptors are membrane proteins composed of five subunits organized around a central aqueous pore. A pentameric channel protein, T 5 M2δ, that emulates the presumed pore‐forming structure of this receptor was generated by assembling five helix‐forming peptide modules at the lysine ϵ‐amino groups of the 11‐residue template [K ∗ AK ∗ KK ∗ PGK ∗ EK ∗ G], where ∗ indicates attachment sites. Helical modules represent the sequence of the M2 segment of the Torpedo californica acetylcholine receptor (AChR) δ subunit; M2 segments are considered involved in pore‐lining. Purified T 5 M2δ migrates in SDS‐PAGE with an apparent M r ~14,000, concordant with a protein of 126 residues. T 5 M2δ forms cation‐selective channels when reconstituted in planar lipid bilayers. The single channel conductance in symmetric 0.5 M K.C1 is 40 pS. This value approximates the 45 pS single channel conductance characteristic of authentic purified Torpedo AChR, recorded under otherwise identical conditions. These results, together with conformational energy calculations, support the notion that a bundle of five amphipathic a‐helices is a plausible structural motif underlying the inner bundle that forms the pore of the pentameric AChR channel.