The minimum M3-M4 loop length of neurotransmitteractivated pentameric receptors is critical for the structural integrity of cytoplasmic portals

Abstract

Background: Residue 436 within 5-HT3A cytoplasmic portals determines single channel conductance (γ) and rectification. Results: M3-M4 loop truncation to 75 residues spared inward rectification; truncation to 70 abolished rectification and increased -. Human Cys-loop neurotransmitter receptor M3-M4 loops all exceed 70 residues. Conclusion: M3-M4 lengths of >70 are critical. Significance: Cytoplasmic portals may be essential for normal function of Cys-loop neurotransmitter receptors. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.