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Constitutively active mutants of 5‐HT 4 receptors are they in unique active states?
Author(s) -
Claeysen Sylvie,
Sebben Michèle,
Bécamel Carine,
Parmentier MarieLaure,
Dumuis Aline,
Bockaert Joël
Publication year - 2001
Publication title -
embo reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.584
H-Index - 184
eISSN - 1469-3178
pISSN - 1469-221X
DOI - 10.1093/embo-reports/kve003
Subject(s) - allosteric regulation , g protein coupled receptor , intracellular , receptor , denaturation (fissile materials) , mutant , biophysics , kinetics , chemistry , intrinsic activity , biochemistry , biology , microbiology and biotechnology , gene , agonist , physics , quantum mechanics , nuclear chemistry
Somatic mutations leading to constitutively active G‐protein coupled receptors (GPCRs) are responsible for certain human diseases. A consistent structural description of the molecular change underlying the conversion of GPCRs from an inactive R state to an active R * state is lacking. Here, we show that a series of constitutively active 5‐HT 4 receptors (mutated or truncated in the C‐terminal and the third intracellular loop) were characterized by an increase in their denaturation rate at 55°C. The thermal denaturation kinetics were monophasic, suggesting that we were measuring mainly the denaturation rate of R * . Analysis of these kinetics revealed that constitutively active C‐terminal domain mutants, were due to a change in the J constant governing the R/R * equilibrium. However, the constitutive activity of the receptor mutated within the third intracellular loop was the result of both a change in the allosteric J constant and a change in the R * conformation.