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α‐Helical distorting substitutions disrupt coupling between m3 muscarinic receptor and G proteins
Author(s) -
Duerson Kevin,
Carroll Reed,
Clapham David
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)81541-7
Subject(s) - alanine , biophysics , receptor , xenopus , muscarinic acetylcholine receptor , 5 ht5a receptor , biology , muscarinic acetylcholine receptor m5 , protein subunit , chemistry , biochemistry , amino acid , muscarinic acetylcholine receptor m3 , gene
Acetylcholine stimulation of the m3 or m2 muscarinic receptor expressed in Xenopus laevis oocytes induces either a fast transient or slowly oscillating calcium‐sensitive chloride current. The speed of these currents reflects the efficiency of receptor coupling to guanine nucleotide‐binding proteins and phosphatidylinositol (PI) turnover. Point mutations of the m3 receptor were made in a region of the third cytoplasmic loop to test whether receptor function relied on an α‐helical structure of the G protein‐coupling domain. Proline substitution for glutamate at position 257 disrupted the m3 response. Also, single alanine insertions between residues 259 and 260 disrupted the m3 receptor‐stimulated response while double alanine insertions at this site had no effect. Based on these results, we suggest that a region of the third cytoplasmic loop of the m3 receptor possesses an amphipathic α‐helical conformation.