Molecular dynamics simulation links conformation of a pore-flanking region to hyperekplexia-related dysfunction of the inhibitory glycine receptor.
Inhibitory glycine receptors mediate rapid synaptic inhibition in mammalian spinal cord and brainstem. The previously identified hyperekplexia mutation GLRA1(P250T), located within the intracellular TM1-2 loop of the GlyR alpha1 subunit, results in altered receptor activation and desensitization. Here, elementary steps of ion channel function of alpha1(250) mutants were resolved and shown to correlate with hydropathy and molar volume of residue alpha1(250). Single-channel recordings and rapid activation kinetic studies using laser pulse photolysis showed reduced conductance but similar open probability of alpha1(P250T) mutant channels. Molecular dynamics simulation of a helix-turn-helix motif representing the intracellular TM1-2 domain revealed alterations in backbone conformation, indicating an increased flexibility in these mutants that paralleled changes in elementary steps of channel function. Thus, the architecture of the TM1-2 loop is a critical determinant of ion channel conductance and receptor desensitization.
Institut für Biochemie, Emil-Fischer-Zentrum, Friedrich-Alexander-Universität, Erlangen-Nürnberg, Erlangen, Germany.
Hans-Georg
HG
Breitinger
Harald
H
Lanig
Christine
C
Vohwinkel
Christof
C
Grewer
Ulrike
U
Breitinger
Tim
T
Clark
Cord-Michael
CM
Becker
D002460:Cell Line; D003198:Computer Simulation; D004305:Dose-Response Relationship, Drug; D005998:Glycine / Q000378:metabolism / Q000494:pharmacology; D019077:Helix-Turn-Helix Motifs / Q000235:genetics; D006801:Humans; D007473:Ion Channels / Q000037:antagonists & inhibitors* / Q000235:genetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009207:Myoclonus / Q000235:genetics* / Q000503:physiopathology; D009433:Neural Inhibition / Q000235:genetics; D018408:Patch-Clamp Techniques; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D018009:Receptors, Glycine / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D013216:Reflex, Startle / Q000235:genetics; D016750:Stiff-Person Syndrome / Q000235:genetics / Q000503:physiopathology; D013816:Thermodynamics
C000657604:GLRA1 protein, human; D007473:Ion Channels; D021122:Protein Subunits; D018009:Receptors, Glycine; D005998:Glycine