Medicine and Health Sciences Commons^™

The Minimum M3-M4 Loop Length Of Neurotransmitter-Activated Pentameric Receptors Is Critical For The Structural Integrity Of Cytoplasmic Portals, Daniel T. Baptista-Hon, Tarek Z. Deeb, Jeremy J. Lambert, John A. Peters, Tim G. Hales

Pharmacology and Physiology Faculty Publications

The 5-HT₃A receptor homology model, based on the partial structure of the nicotinic acetylcholine receptor from Torpedo marmorata, reveals an asymmetric ion channel with five portals framed by adjacent helical amphipathic (HA) stretches within the 114-residue loop between the M3 and M4 membrane-spanning domains. The positive charge of Arg-436, located within the HA stretch, is a rate-limiting determinant of single channel conductance (γ). Further analysis reveals that positive charge and volume of residue 436 are determinants of 5-HT₃A receptor inward rectification, exposing an additional role for portals. A structurally unresolved stretch of 85 residues constitutes …