Premium
A ring of uncharged polar amino acids as a component of channel constriction in the nicotinic acetylcholine receptor
Author(s) -
Imoto Keiji,
Konno Takashi,
Nakai Junichi,
Wang Feng,
Mishina Masayoshi,
Numa Shosaku
Publication year - 1991
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(91)81068-j
Subject(s) - acetylcholine receptor , chemistry , torpedo , nicotinic acetylcholine receptor , protein subunit , biophysics , transmembrane protein , cys loop receptors , threonine , xenopus , cytoplasm , stereochemistry , nicotinic agonist , transmembrane domain , acetylcholine , amino acid , receptor , biochemistry , serine , biology , endocrinology , enzyme , gene
The channel pore of the nicotinic acetylcholine receptor (AChR) has been investigated by analysing single‐channel conductances of systematically mutated Torpedo receptors expressed in Xenopus oocytes. The mutations mainly alter the size and polarity of uncharged polar amino acid residues of the acetylcholine receptor subunits positioned between the cytoplasmic ring and the extracellular ring. From the results obtained, we conclude that a ring of uncharged polar residues comprising threonine 244 of the α‐subunit (αT244), βS250, γT253 and δS258 (referred to as the central ring) and the anionic intermediate ring, which are adjacent to each other in the assumed α‐helical configuration of the M2‐containing transmembrane segment, together form a narrow channel constriction of short length, located close to the cytoplasmic side of the membrane. Our results also suggest that individual subunits, particularly the γ‐subunit, are asymmetrically positioned at the channel constriction.