Referenced in: none

Automatically associated channels: Kir2.3 , Slo1

Title: Alpha-helical distorting substitution disrupt coupling between m3 muscarinic receptor and G proteins.

Authors: K Duerson, R Carroll, D Clapham

Journal, date & volume: FEBS Lett., 1993 Jun 7 , 324, 103-8

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/7684986

Abstract
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 alpha-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 alpha-helical conformation.