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Dynamic control of Allosteric Inhibitor Specificity for RGS4
Author(s) -
Storaska Andrew John,
Vashitsh Harish,
Neubig Richard R
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.1095.11
Subject(s) - allosteric regulation , g protein coupled receptor , g protein , protein subunit , chemistry , alanine scanning , biophysics , binding site , helix bundle , regulator of g protein signaling , small molecule , biochemistry , protein structure , microbiology and biotechnology , receptor , biology , gtpase activating protein , mutation , mutagenesis , gene
G‐protein coupled receptors (GPCRs) are critically regulated through downstream protein‐protein interactions including Regulator of G‐protein signaling (RGS)‐proteins. They suppress GPCR output by enhancing the rate of GTP hydrolysis on the Gα subunit. A nM potency inhibitor (CCG‐50014) is several hundred‐fold selective for RGS4 over other RGS proteins. Like previous RGS inhibitors, CCG‐50014 depends on covalent cysteine modification for activity. Two key cysteines‐(95 and 148) are buried in an allosteric site. We hypothesized that inhibitor interaction at cys 95 or 148 alters the packing of alpha helices 4, 5, 6 and 7 to disrupt G‐protein binding. Consistent with this hypothesis, HSQC‐NMR experiments using RGS4 containing only Cys 95, in the presence of CCG‐50014, shows perturbations clustering in the helix bundle and in the G‐protein binding site. Molecular dynamics simulations predict motions that would provide inhibitor access to the buried allosteric cysteines, and open a novel cryptic pocket into which small molecules could be targeted. Binding of CCG‐50014 likely stabilizes a more open confirmation resulting in disruption of the G‐protein binding interface. Differences among RGS proteins involving these conformational transitions may drive the observed inhibitor selectivity for RGS4. (Supported by NIH T32 GM007767 and R01DA023253)