scholarly journals Allosteric binding site in a Cys-loop receptor ligand-binding domain unveiled in the crystal structure of ELIC in complex with chlorpromazine

2016 ◽  
Vol 113 (43) ◽  
pp. E6696-E6703 ◽  
Author(s):  
Mieke Nys ◽  
Eveline Wijckmans ◽  
Ana Farinha ◽  
Özge Yoluk ◽  
Magnus Andersson ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Ion Channel ◽  
Binding Site ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Channel Pore ◽  
X Ray ◽  
Electrophysiological Recordings ◽  
Channel Opening ◽  
Dynamics Simulations

Pentameric ligand-gated ion channels or Cys-loop receptors are responsible for fast inhibitory or excitatory synaptic transmission. The antipsychotic compound chlorpromazine is a widely used tool to probe the ion channel pore of the nicotinic acetylcholine receptor, which is a prototypical Cys-loop receptor. In this study, we determine the molecular determinants of chlorpromazine binding in the Erwinia ligand-gated ion channel (ELIC). We report the X-ray crystal structures of ELIC in complex with chlorpromazine or its brominated derivative bromopromazine. Unexpectedly, we do not find a chlorpromazine molecule in the channel pore of ELIC, but behind the β8–β9 loop in the extracellular ligand-binding domain. The β8–β9 loop is localized downstream from the neurotransmitter binding site and plays an important role in coupling of ligand binding to channel opening. In combination with electrophysiological recordings from ELIC cysteine mutants and a thiol-reactive derivative of chlorpromazine, we demonstrate that chlorpromazine binding at the β8–β9 loop is responsible for receptor inhibition. We further use molecular-dynamics simulations to support the X-ray data and mutagenesis experiments. Together, these data unveil an allosteric binding site in the extracellular ligand-binding domain of ELIC. Our results extend on previous observations and further substantiate our understanding of a multisite model for allosteric modulation of Cys-loop receptors.

scholarly journals X-ray Structures of Progesterone Receptor Ligand Binding Domain in Its Agonist State Reveal Differing Mechanisms for Mixed Profiles of 11β-Substituted Steroids

2012 ◽  
Vol 287 (24) ◽  
pp. 20333-20343 ◽  
Author(s):  
Scott J. Lusher ◽  
Hans C. A. Raaijmakers ◽  
Diep Vu-Pham ◽  
Bert Kazemier ◽  
Rolien Bosch ◽  
...  
Keyword(s):  
Progesterone Receptor ◽  
Ligand Binding ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Receptor Ligand ◽  
X Ray

Structure of the activation domain of the GM-CSF/IL-3/IL-5 receptor common β-chain bound to an antagonist

Blood ◽  
2000 ◽  
Vol 95 (8) ◽  
pp. 2491-2498 ◽  
Author(s):  
Jamie Rossjohn ◽  
William J. McKinstry ◽  
Joanna M. Woodcock ◽  
Barbara J. McClure ◽  
Timothy R. Hercus ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Binding Site ◽  
Interleukin 2 ◽  
Receptor Activation ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Fab Fragment ◽  
Gm Csf ◽  
Single Receptor ◽  
Β Chain

Abstract Heterodimeric cytokine receptors generally consist of a major cytokine-binding subunit and a signaling subunit. The latter can transduce signals by more than 1 cytokine, as exemplified by the granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-2 (IL-2), and IL-6 receptor systems. However, often the signaling subunits in isolation are unable to bind cytokines, a fact that has made it more difficult to obtain structural definition of their ligand-binding sites. This report details the crystal structure of the ligand-binding domain of the GM-CSF/IL-3/IL-5 receptor β-chain (βc) signaling subunit in complex with the Fab fragment of the antagonistic monoclonal antibody, BION-1. This is the first single antagonist of all 3 known eosinophil-producing cytokines, and it is therefore capable of regulating eosinophil-related diseases such as asthma. The structure reveals a fibronectin type III domain, and the antagonist-binding site involves major contributions from the loop between the B and C strands and overlaps the cytokine-binding site. Furthermore, tyrosine421 (Tyr421), a key residue involved in receptor activation, lies in the neighboring loop between the F and G strands, although it is not immediately adjacent to the cytokine-binding residues in the B-C loop. Interestingly, functional experiments using receptors mutated across these loops demonstrate that they are cooperatively involved in full receptor activation. The experiments, however, reveal subtle differences between the B-C loop and Tyr421, which is suggestive of distinct functional roles. The elucidation of the structure of the ligand-binding domain of βc also suggests how different cytokines recognize a single receptor subunit, which may have implications for homologous receptor systems.

scholarly journals Characterization of the Nurr1 ligand-binding domain co-activator interaction surface

2006 ◽  
Vol 37 (2) ◽  
pp. 317-326 ◽  
Author(s):  
Nikolaos Volakakis ◽  
Michal Malewicz ◽  
Banafsheh Kadkhodai ◽  
Thomas Perlmann ◽  
Gerard Benoit
Keyword(s):  
Ligand Binding ◽  
Binding Site ◽  
Close Association ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Site Directed Mutagenesis ◽  
Orphan Nuclear Receptor ◽  
Hydrophobic Region ◽  
Binding Surface

The recently solved crystal structure of the orphan nuclear receptor (NR) Nurr1 ligand-binding domain (LBD) showed that Nurr1 lacks a cavity for ligand binding and a canonical NR co-activator-binding site. Computer modeling of the Nurr1 LBD structure identified a hydrophobic region on the surface of the Nurr1 LBD that was positioned on the opposite side from the classical co-activator-binding site. Site-directed mutagenesis demonstrated that this region is critical for the activity of the Nurr1 LBD. Most mutations introduced in this region reduced or abolished transcriptional activity of the Nurr1 LBD, but mutation at lysine (K577) resulted in a drastically increased activity. Moreover, the activity of the Nurr1 LBD was shown to correlate with a propensity for proteasome-dependent degradation revealing a close association between activity and Nurr1 protein turnover. These data provide novel insights into the mechanisms of transcription via the Nurr1 LBD and identify an alternative co-activator-binding surface that is unique to the NR4A family of NRs.

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