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Int J Parasitol Drugs Drug Resist
2018 Dec 01;83:534-539. doi: 10.1016/j.ijpddr.2018.10.001.
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A mutational and molecular dynamics study of the cys-loop GABA receptor Hco-UNC-49 from Haemonchus contortus: Agonist recognition in the nematode GABA receptor family.
Foster J
,
Cochrane E
,
Khatami MH
,
Habibi SA
,
de Haan H
,
Forrester SG
.
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The UNC-49 receptor is a unique nematode γ-aminobutyric acid (GABA)-gated chloride channel that may prove to be a novel target for the development of nematocides. Here we have characterized various charged amino acid residues in and near the agonist binding site of the UNC-49 receptor from the parasitic nematode Haemonchus contorts. Utilizing the Caenorhabditis elegans GluCl crystal structure as a template, a model was generated and various charged residues [D83 (loop D), E131 (loop A), H137 (pre-loop E), R159 (Loop E), E185 (Loop B) and R241 (Loop C)] were investigated based on their location and conservation. These residues may contribute to structure, function, and molecular interactions with agonists. It was found that all residues chosen were important for receptor function to varying degrees. Results of the mutational analysis and molecular simulations suggest that R159 may be interacting with D83 by an ionic interaction that may be crucial for general GABA receptor function. We have used the results from this study as well as knowledge of residues involved in GABA receptor binding to identify sequence patterns that may assist in understanding the function of lesser known GABA receptor subunits from parasitic nematodes.
Fig. 1. (A) Model of Hco-UNC-49B homodimer with docked GABA molecule with residues that were examined in this study. Representative distances are shown in angstroms (B) Sequence alignment of the location of the residues within the major binding loops. The various binding loops corresponding to each residue are indicated by color coding. Residues examined in this study are indicated by * (C) Representative electrophysiological tracings of Hco-UNC-49BC with alanine mutated UNC-49B subunits D83A, E131A, E185A, H137A, R159A, R241A (D) Dose-response curves of all functional Hco-UNC-49B alanine mutants showing differences in GABA sensitivity, with normalized currents. Each point represents a mean ± SE (n ≥ 5). Residue numbering refers to the first methionine in the Hco-UNC-49B subunit (EU939734.1). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)
Fig. 2. Dose-response curves of D83 mutations of Hco-UNC-49B in comparison to WT showing differences in GABA sensitivity, with normalized currents. Each point represents a mean ± SE (n ≥ 5).
Fig. 3. Molecular simulations of residue interactions in the Hco-UNC-49 receptor. (A) Interactions between E185 and R241 over the course of the simulation. (B) Interactions between D83 and R159 over the course of the simulation. Insets: snapshots of the residues during the simulation. Dashed lines represent distances ≤3 Å. The bonds with the shortest distance are used to calculate bond percentages.
Fig. 4. Sequence alignment of the major binding loop of Hco-UNC-49B with other Cys-loop GABA receptors. The amino acid residues mutated in this study is indicated by (●) and are numbered above. Residues discussed that are important for agonist recognition described in Table 2 are indicated by (★).
Fig. 5. Molecular model of Hco-UNC-49 homodimer with GABA docked. The residues ERRS and their positions are indicated.
Abdelmassih,
Evaluating the longevity of surgically extracted Xenopus laevis oocytes for the study of nematode ligand-gated ion channels.
2017, Pubmed
Abdelmassih,
Evaluating the longevity of surgically extracted Xenopus laevis oocytes for the study of nematode ligand-gated ion channels.
2017,
Pubmed
Accardi,
The Haemonchus contortus UNC-49B subunit possesses the residues required for GABA sensitivity in homomeric and heteromeric channels.
2011,
Pubmed
Accardi,
Nematode cys-loop GABA receptors: biological function, pharmacology and sites of action for anthelmintics.
2012,
Pubmed
Ashby,
GABA binding to an insect GABA receptor: a molecular dynamics and mutagenesis study.
2012,
Pubmed
Bamber,
Pharmacological characterization of the homomeric and heteromeric UNC-49 GABA receptors in C. elegans.
2003,
Pubmed
Bamber,
The Caenorhabditis elegans unc-49 locus encodes multiple subunits of a heteromultimeric GABA receptor.
1999,
Pubmed
Beech,
Nematode parasite genes: what's in a name?
2010,
Pubmed
Beg,
EXP-1 is an excitatory GABA-gated cation channel.
2003,
Pubmed
Bergmann,
A unified model of the GABA(A) receptor comprising agonist and benzodiazepine binding sites.
2013,
Pubmed
Best,
Optimization of the additive CHARMM all-atom protein force field targeting improved sampling of the backbone φ, ψ and side-chain χ(1) and χ(2) dihedral angles.
2012,
Pubmed
Feng,
Study of the nematode putative GABA type-A receptor subunits: evidence for modulation by ivermectin.
2002,
Pubmed
Hibbs,
Principles of activation and permeation in an anion-selective Cys-loop receptor.
2011,
Pubmed
Holden-Dye,
Anthelmintic drugs and nematicides: studies in Caenorhabditis elegans.
2014,
Pubmed
Humphrey,
VMD: visual molecular dynamics.
1996,
Pubmed
Irwin,
ZINC: a free tool to discover chemistry for biology.
2012,
Pubmed
Jones,
The cys-loop ligand-gated ion channel gene superfamily of the nematode, Caenorhabditis elegans.
2008,
Pubmed
Kaji,
A molecular characterization of the agonist binding site of a nematode cys-loop GABA receptor.
2015,
Pubmed
Kwaka,
Molecular Characterization of Binding Loop E in the Nematode Cys-Loop GABA Receptor.
2018,
Pubmed
Lynagh,
Principles of agonist recognition in Cys-loop receptors.
2014,
Pubmed
Miller,
Crystal structure of a human GABAA receptor.
2014,
Pubmed
Newell,
Mutation of glutamate 155 of the GABAA receptor beta2 subunit produces a spontaneously open channel: a trigger for channel activation.
2004,
Pubmed
Sali,
Comparative protein modelling by satisfaction of spatial restraints.
1993,
Pubmed
Siddiqui,
An UNC-49 GABA receptor subunit from the parasitic nematode Haemonchus contortus is associated with enhanced GABA sensitivity in nematode heteromeric channels.
2010,
Pubmed
Siddiqui,
Hco-LGC-38 is novel nematode cys-loop GABA receptor subunit.
2012,
Pubmed
Trott,
AutoDock Vina: improving the speed and accuracy of docking with a new scoring function, efficient optimization, and multithreading.
2010,
Pubmed
Vanommeslaeghe,
Automation of the CHARMM General Force Field (CGenFF) I: bond perception and atom typing.
2012,
Pubmed
Vanommeslaeghe,
CHARMM general force field: A force field for drug-like molecules compatible with the CHARMM all-atom additive biological force fields.
2010,
Pubmed
Vanommeslaeghe,
Automation of the CHARMM General Force Field (CGenFF) II: assignment of bonded parameters and partial atomic charges.
2012,
Pubmed
Wolstenholme,
Ion channels and receptor as targets for the control of parasitic nematodes.
2011,
Pubmed
Yu,
Extension of the CHARMM General Force Field to sulfonyl-containing compounds and its utility in biomolecular simulations.
2012,
Pubmed
