Article

Cis-trans isomerization at a proline opens the pore of a neurotransmitter-gated ion channel.

Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK.
Nature (Impact Factor: 42.35). 12/2005; 438(7065):248-52. DOI: 10.1038/nature04130
Source: PubMed

ABSTRACT 5-hydroxytryptamine type 3 (5-HT3) receptors are members of the Cys-loop receptor superfamily. Neurotransmitter binding in these proteins triggers the opening (gating) of an ion channel by means of an as-yet-uncharacterized conformational change. Here we show that a specific proline (Pro 8*), located at the apex of the loop between the second and third transmembrane helices (M2-M3), can link binding to gating through a cis-trans isomerization of the protein backbone. Using unnatural amino acid mutagenesis, a series of proline analogues with varying preference for the cis conformer was incorporated at the 8* position. Proline analogues that strongly favour the trans conformer produced non-functional channels. Among the functional mutants there was a strong correlation between the intrinsic cis-trans energy gap of the proline analogue and the activation of the channel, suggesting that cis-trans isomerization of this single proline provides the switch that interconverts the open and closed states of the channel. Consistent with this proposal, nuclear magnetic resonance studies on an M2-M3 loop peptide reveal two distinct, structured forms. Our results thus confirm the structure of the M2-M3 loop and the critical role of Pro 8* in the 5-HT3 receptor. In addition, they suggest that a molecular rearrangement at Pro 8* is the structural mechanism that opens the receptor pore.

0 Followers
 · 
277 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Prolyl cis/trans isomerizations have long been known as critical and rate-limiting steps in protein folding. More recently, it became clear that they are also used as slow conformational switches and molecular timers in the regulation of protein activity. Here we describe several such proline switches, how they are regulated and how prolyl isomerizations can function as attenuators and provide allosteric systems with a molecular memory. This article is part of a Special Issue entitled Proline-directed Foldases: Cell Signaling Catalysts and Drug Targets.
    Biochimica et Biophysica Acta (BBA) - General Subjects 12/2014; DOI:10.1016/j.bbagen.2014.12.019 · 3.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 1-Azatricyclo[3.3.1.13,7]decan-2-one (3), the parent compound of a rare class of 90° twisted amides, has finally been synthesized, using an unprecedented transformation. These compounds are of special interest as transition state mimics for the enzyme-catalysed cis-trans rotamer interconversion of amides involved in peptide and protein folding and function. The stabilization of the amide group in its high energy, perpendicular conformation common to both systems is shown for the rigid tricyclic system to depend, as predicted by calculation.
    Journal of the American Chemical Society 12/2014; DOI:10.1021/ja511460a · 11.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Prolyl isomerizations are intrinsically slow processes. They determine the rates of many protein folding reactions and control regulatory events in folded proteins. Prolyl isomerases are able to catalyze these isomerizations, and thus they have the potential to assist protein folding and to modulate protein function. Here we provide examples for how prolyl isomerizations limit protein folding and are accelerated by prolyl isomerases, and how native-state prolyl isomerizations regulate protein functions. The roles of prolines in protein folding and protein function are closely interrelated because they both depend on the coupling between cis/trans isomerization and conformational changes that can involve extended regions of a protein. Copyright © 2015. Published by Elsevier Ltd.
    Journal of Molecular Biology 02/2015; DOI:10.1016/j.jmb.2015.01.023 · 3.96 Impact Factor

Full-text (2 Sources)

Download
211 Downloads
Available from
May 17, 2014