Evidence for a common mechanism of SIRT1 regulation by allosteric activators.
Ontology highlight
ABSTRACT:
SUBMITTER: Hubbard BP
PROVIDER: S-EPMC3799917 | biostudies-literature | 2013 Mar
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:We present a common allosteric mechanism for control of inflammatory and apoptotic caspases. Highly specific thiol-containing inhibitors of the human inflammatory caspase-1 were identified by using disulfide trapping, a method for site-directed small-molecule discovery. These compounds became trapped by forming a disulfide bond with a cysteine residue in the cavity at the dimer interface approximately 15 A away from the active site. Mutational and structural analysis uncovered a linear circuit of functional residues that runs from one active site through the allosteric cavity and into the second active site. Kinetic analysis revealed robust positive cooperativity not seen in other endopeptidases. Recently, disulfide trapping identified a similar small-molecule site and allosteric transition in the apoptotic caspase-7 that shares only a 23% sequence identity with caspase-1. Together, these studies show a general small-molecule-binding site for functionally reversing the zymogen activation of caspases and suggest a common regulatory site for the allosteric control of inflammation and apoptosis.
| S-EPMC1458511 | biostudies-literature
Project description:The recent discovery of activator compounds binding to an allosteric site on the NAD+-dependent protein lysine deacetylase, sirtuin 6 (SIRT6) has attracted interest and presents a pharmaceutical target for aging-related and cancer diseases. However, the mechanism underlying allosteric activation of SIRT6 by the activator MDL-801 remains largely elusive because no major conformational changes are observed upon activator binding. By combining molecular dynamics simulations with biochemical and kinetic analyses of wild-type SIRT6 and its variant M136A, we show that conformational rotation of 2-methyl-4-fluoro-5-bromo substituent on the right phenyl ring (R-ring) of MDL-801, which uncovers previously unseen hydrophobic interactions, contributes to increased activating deacetylation activity of SIRT6. This hypothesis is further supported by the two newly synthesized MDL-801 derivatives through the removal of the 5-Br atom on the R-ring (MDL-801-D1) or the restraint of the rotation of the R-ring (MDL-801-D2). We further propose that the 5-Br atom serves as an allosteric driver that controls the ligand allosteric efficacy. Our study highlights the effect of allosteric enzyme catalytic activity by activator binding and provides a rational approach for enhancing deacetylation activity.
| S-EPMC8148055 | biostudies-literature
Project description:Glucokinase (GK) is a glucose-phosphorylating enzyme that regulates insulin release and hepatic metabolism, and its loss of function is implicated in diabetes pathogenesis. GK activators (GKAs) are attractive therapeutics in diabetes; however, clinical data indicate that their benefits can be offset by hypoglycemia, owing to marked allosteric enhancement of the enzyme's glucose affinity. We show that a phosphomimetic of the BCL-2 homology 3 (BH3) α-helix derived from human BAD, a GK-binding partner, increases the enzyme catalytic rate without dramatically changing glucose affinity, thus providing a new mechanism for pharmacologic activation of GK. Remarkably, BAD BH3 phosphomimetic mediates these effects by engaging a new region near the enzyme's active site. This interaction increases insulin secretion in human islets and restores the function of naturally occurring human GK mutants at the active site. Thus, BAD phosphomimetics may serve as a new class of GKAs.
| S-EPMC4084830 | biostudies-literature
Project description:Allosteric regulation is protein activation by effector binding at a site other than the active site. Here, we show via X-ray structural analysis of gibberellin 2-oxidase 3 (GA2ox3), and auxin dioxygenase (DAO), that such a mechanism maintains hormonal homeostasis in plants. Both enzymes form multimers by interacting via GA4 and indole-3-acetic acid (IAA) at their binding interface. Via further functional analyses we reveal that multimerization of these enzymes gradually proceeds with increasing GA4 and IAA concentrations; multimerized enzymes have higher specific activities than monomer forms, a system that should favour the maintenance of homeostasis for these phytohormones. Molecular dynamic analysis suggests a possible mechanism underlying increased GA2ox3 activity by multimerization-GA4 in the interface of oligomerized GA2ox3s may be able to enter the active site with a low energy barrier. In summary, homeostatic systems for maintaining GA and IAA levels, based on a common allosteric mechanism, appear to have developed independently.
| S-EPMC7195466 | biostudies-literature
Project description:Allosteric regulation is a fundamental mechanism of biological control. Here, we investigated the allosteric mechanism by which GTP inhibits cross-linking activity of transglutaminase 2 (TG2), a multifunctional protein, with postulated roles in receptor signaling, extracellular matrix assembly, and apoptosis. Our findings indicate that at least two components are involved in functionally coupling the allosteric site and active center of TG2, namely (i) GTP binding to mask a conformationally destabilizing switch residue, Arg-579, and to facilitate interdomain interactions that promote adoption of a compact, catalytically inactive conformation and (ii) stabilization of the inactive conformation by an uncommon H bond between a cysteine (Cys-277, an active center residue) and a tyrosine (Tyr-516, a residue located on a loop of the beta-barrel 1 domain that harbors the GTP-binding site). Although not essential for GTP-mediated inhibition of cross-linking, this H bond enhances the rate of formation of the inactive conformer.
| S-EPMC1750866 | biostudies-literature
Project description:We have previously reported that distinctly different concentrations of GDP stimulate the phosphorylation and dephosphorylation of p36, the alpha-subunit of succinyl-CoA synthetase (SCS) in Dictyostelium discoideum. In this present study, we have investigated the mechanism underlying these dual effects of GDP. Dephosphorylation of p36 is induced by relatively high levels of GDP and is coincident with the formation of GTP. This indicates that, at high concentrations, GDP serves as a substrate of SCS. However, 100-fold lower concentrations of GDP, which do not bind to the catalytic site to induce SCS dephosphorylation, stimulate p36 phosphorylation. This stimulation is not diminished by dilution of the sample, and is retained during purification of the protein. Gel-filtration analyses indicate that SCS in our system behaves as a non-interacting alpha beta dimer, the hydrodynamic behaviour of which is not altered by the presence of added GDP. The data indicate that altered protein-protein interactions do not account for the stimulation of p36 phosphorylation by low GDP concentrations. We propose that GDP functions as an allosteric regulator of SCS, and experiments using guanosine 5'-[beta-thio]diphosphate (GDP[S]) are shown to distinguish further the allosteric and catalytic binding sites.
| S-EPMC1134635 | biostudies-other
Project description:Antithrombin, a plasma glycoprotein serpin, requires conformational activation by heparin to induce an anticoagulant effect, which is mediated through accelerated factor Xa inhibition. Heparin, a highly charged polymer and an allosteric activator of the serpin, is associated with major adverse effects. To design better, but radically different activators of antithrombin from heparin, we utilized a pharmacophore-based approach. A tetrahydroisoquinoline-based scaffold was designed to mimic four critical anionic groups of the key trisaccharide DEF constituting the sequence-specific pentasaccharide DEFGH in heparin. Activator IAS(5) containing 5,6-disulfated tetrahydroisoquinoline and 3,4,5-trisulfated phenyl rings was found to bind antithrombin at pH 7.4 with an affinity comparable to the reference trisaccharide DEF. IAS(5) activated the inhibitor nearly 30-fold, nearly 2- to 3-fold higher than our first generation flavanoid-based designs. This work advances the concept of antithrombin activation through non-saccharide, organic molecules and pinpoints a direction for the design of more potent molecules.
| S-EPMC2743457 | biostudies-literature
Project description:Oxysterols are a class of endogenous signaling molecules that can activate the Hedgehog pathway, which has critical roles in development, regeneration and cancer. However, it has been unclear how oxysterols influence Hedgehog signaling, including whether their effects are mediated through a protein target or indirectly through effects on membrane properties. To answer this question, we synthesized the enantiomer and an epimer of the most potent oxysterol, 20(S)-hydroxycholesterol. Using these molecules, we show that the effects of oxysterols on Hedgehog signaling are exquisitely stereoselective, consistent with the hypothesis that they function through a specific protein target. We present several lines of evidence that this protein target is the seven-pass transmembrane protein Smoothened, a major drug target in oncology. Our work suggests that these enigmatic sterols, which have multiple effects on cell physiology, may act as ligands for signaling receptors and provides a generally applicable framework for probing sterol signaling mechanisms.
| S-EPMC3262054 | biostudies-literature
Project description:The proteasome, a complex multi-catalytic protease machinery, orchestrates the protein degradation essential for maintaining cellular homeostasis, and its dysregulation also underlies many different types of diseases. Its function is regulated by many different mechanisms that encompass various factors such as proteasome activators (PAs), adaptor proteins, and post-translational modifications. This review highlights the unique characteristics of proteasomal regulation through the lens of a distinct family of regulators, the 11S, REGs, or PA26/PA28. This ATP-independent family, spanning from amoebas to mammals, exhibits a common architectural structure; yet, their cellular biology and criteria for protein degradation remain mostly elusive. We delve into their evolution and cellular biology, and contrast their structure and function comprehensively, emphasizing the unanswered questions regarding their regulatory mechanisms and broader roles in proteostasis. A deeper understanding of these processes will illuminate the roles of this regulatory family in biology and disease, thus contributing to the advancement of therapeutic strategies.
| S-EPMC10526260 | biostudies-literature
Project description:Drugs targeting the orthosteric, primary binding site of G protein-coupled receptors are the most common therapeutics. Allosteric binding sites, elsewhere on the receptors, are less well-defined, and so less exploited clinically. We report the crystal structure of the prototypic ?2-adrenergic receptor in complex with an orthosteric agonist and compound-6FA, a positive allosteric modulator of this receptor. It binds on the receptor's inner surface in a pocket created by intracellular loop 2 and transmembrane segments 3 and 4, stabilizing the loop in an ?-helical conformation required to engage the G protein. Structural comparison explains the selectivity of the compound for ?2- over the ?1-adrenergic receptor. Diversity in location, mechanism, and selectivity of allosteric ligands provides potential to expand the range of receptor drugs.
| S-EPMC6705129 | biostudies-literature