scholarly journals Structural basis of rifampin inactivation by rifampin phosphotransferase

2016 ◽  
Vol 113 (14) ◽  
pp. 3803-3808 ◽  
Author(s):  
Xiaofeng Qi ◽  
Wei Lin ◽  
Miaolian Ma ◽  
Chengyuan Wang ◽  
Yang He ◽  
...  
Keyword(s):  
Molecular Mechanism ◽  
Conformational Changes ◽  
Bacterial Infections ◽  
Binding Pocket ◽  
Resistance Mechanisms ◽  
Binding Domain ◽  
Structural Basis ◽  
Atp Binding ◽  
Toggle Switch ◽  
The Cost

Rifampin (RIF) is a first-line drug used for the treatment of tuberculosis and other bacterial infections. Various RIF resistance mechanisms have been reported, and recently an RIF-inactivation enzyme, RIF phosphotransferase (RPH), was reported to phosphorylate RIF at its C21 hydroxyl at the cost of ATP. However, the underlying molecular mechanism remained unknown. Here, we solve the structures of RPH from Listeria monocytogenes (LmRPH) in different conformations. LmRPH comprises three domains: an ATP-binding domain (AD), an RIF-binding domain (RD), and a catalytic His-containing domain (HD). Structural analyses reveal that the C-terminal HD can swing between the AD and RD, like a toggle switch, to transfer phosphate. In addition to its catalytic role, the HD can bind to the AD and induce conformational changes that stabilize ATP binding, and the binding of the HD to the RD is required for the formation of the RIF-binding pocket. A line of hydrophobic residues forms the RIF-binding pocket and interacts with the 1-amino, 2-naphthol, 4-sulfonic acid and naphthol moieties of RIF. The R group of RIF points toward the outside of the pocket, explaining the low substrate selectivity of RPH. Four residues near the C21 hydroxyl of RIF, His825, Arg666, Lys670, and Gln337, were found to play essential roles in the phosphorylation of RIF; among these the His825 residue may function as the phosphate acceptor and donor. Our study reveals the molecular mechanism of RIF phosphorylation catalyzed by RPH and will guide the development of a new generation of rifamycins.

scholarly journals Different conformational responses of the β2-adrenergic receptor-Gs complex upon binding of the partial agonist salbutamol or the full agonist isoprenaline

2020 ◽  
Author(s):  
Fan Yang ◽  
Shenglong Ling ◽  
Yingxin Zhou ◽  
Yanan Zhang ◽  
Pei Lv ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Hydrophobic Interactions ◽  
Partial Agonist ◽  
Binding Pocket ◽  
Structural Basis ◽  
Spectroscopic Techniques ◽  
Toggle Switch ◽  
Intracellular Loop ◽  
Full Agonist ◽  
Β2 Adrenergic Receptor

Abstract GPCRs are responsible for most cytoplasmic signaling in response to extracellular ligands with different efficacy profiles. Various spectroscopic techniques have identified that agonists exhibiting varying efficacies can selectively stabilize a specific conformation of the receptor. However, the structural basis for activation of the GPCR-G protein complex by ligands with different efficacies is incompletely understood. To better understand the structural basis underlying the mechanisms by which ligands with varying efficacies differentially regulate the conformations of receptors and G proteins, we determined the structures of β2AR-Gαs$\beta $γ bound with partial agonist salbutamol or bound with full agonist isoprenaline using single-particle cryo-electron microscopy at resolutions of 3.26 Å and 3.80 Å, respectively. Structural comparisons between the β2AR-Gs-salbutamol and β2AR-Gs-isoprenaline complexes demonstrated that the decreased binding affinity and efficacy of salbutamol compared with those of isoprenaline might be attributed to the weakened hydrogen bonding interactions, attenuated hydrophobic interactions in the orthosteric binding pocket and different conformational changes in the rotamer toggle switch in TM6. Moreover, the observed stronger interactions between the intracellular loop 2 or 3 (ICL2 or ICL3) of β2AR and Gαs with the binding of salbutamol versus isoprenaline might decrease phosphorylation in the salbutamol-activated β2AR-Gs complex. From the observed structural differences between these complexes of β2AR, a mechanism of β2AR activation by partial and full agonists is proposed to shed structural insights for β2AR desensitization.

scholarly journals Structural basis for subtype-specific inhibition of the P2X7 receptor

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Akira Karasawa ◽  
Toshimitsu Kawate
Keyword(s):  
P2x7 Receptor ◽  
Hydrophobic Interactions ◽  
Binding Pocket ◽  
Drug Binding ◽  
Structural Basis ◽  
Atp Binding ◽  
Allosteric Site ◽  
Channel Opening ◽  
A Site ◽  
Novel Drug

The P2X7 receptor is a non-selective cation channel activated by extracellular adenosine triphosphate (ATP). Chronic activation of P2X7 underlies many health problems such as pathologic pain, yet we lack effective antagonists due to poorly understood mechanisms of inhibition. Here we present crystal structures of a mammalian P2X7 receptor complexed with five structurally-unrelated antagonists. Unexpectedly, these drugs all bind to an allosteric site distinct from the ATP-binding pocket in a groove formed between two neighboring subunits. This novel drug-binding pocket accommodates a diversity of small molecules mainly through hydrophobic interactions. Functional assays propose that these compounds allosterically prevent narrowing of the drug-binding pocket and the turret-like architecture during channel opening, which is consistent with a site of action distal to the ATP-binding pocket. These novel mechanistic insights will facilitate the development of P2X7-specific drugs for treating human diseases.

scholarly journals Identification of a novel post-hydrolytic state in CFTR gating

2012 ◽  
Vol 139 (5) ◽  
pp. 359-370 ◽  
Author(s):  
Kang-Yang Jih ◽  
Yoshiro Sohma ◽  
Min Li ◽  
Tzyh-Chang Hwang
Keyword(s):  
Free Energy ◽  
Chloride Channel ◽  
Atp Hydrolysis ◽  
Binding Pocket ◽  
Fast Response ◽  
Structural Basis ◽  
Atp Binding ◽  
Closed State ◽  
Binding Domains ◽  
Abc Protein

Adenosine triphosphate (ATP)-binding cassette (ABC) transporters, ubiquitous proteins found in all kingdoms of life, catalyze substrates translocation across biological membranes using the free energy of ATP hydrolysis. Cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of this superfamily in that it functions as an ATP-gated chloride channel. Despite difference in function, recent studies suggest that the CFTR chloride channel and the exporter members of the ABC protein family may share an evolutionary origin. Although ABC exporters harness the free energy of ATP hydrolysis to fuel a transport cycle, for CFTR, ATP-induced dimerization of its nucleotide-binding domains (NBDs) and subsequent hydrolysis-triggered dimer separation are proposed to be coupled, respectively, to the opening and closing of the gate in its transmembrane domains. In this study, by using nonhydrolyzable ATP analogues, such as pyrophosphate or adenylyl-imidodiphosphate as baits, we captured a short-lived state (state X), which distinguishes itself from the previously identified long-lived C2 closed state by its fast response to these nonhydrolyzable ligands. As state X is caught during the decay phase of channel closing upon washout of the ligand ATP but before the channel sojourns to the C2 closed state, it likely emerges after the bound ATP in the catalysis-competent site has been hydrolyzed and the hydrolytic products have been released. Thus, this newly identified post-hydrolytic state may share a similar conformation of NBDs as the C2 closed state (i.e., a partially separated NBD and a vacated ATP-binding pocket). The significance of this novel state in understanding the structural basis of CFTR gating is discussed.

scholarly journals Structural Basis of Vitamin K Antagonism

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 482-482
Author(s):  
Weikai Li ◽  
Shixuan Liu ◽  
Shuang Li
Keyword(s):  
Vitamin K ◽  
Conformational Changes ◽  
Conflicts Of Interest ◽  
Bone Mineralization ◽  
Vitamin K Antagonists ◽  
Membrane Surface ◽  
Warfarin Dose ◽  
Binding Pocket ◽  
Structural Basis ◽  
Vitamin K Cycle

The vitamin K cycle supports blood coagulation, bone mineralization, and vascular calcium homeostasis. A key enzyme in this cycle, vitamin K epoxide reductase (VKOR), is the target of vitamin K antagonists (VKAs). Despite their extensive clinical use, the dose of VKAs (e.g., warfarin) is hard to regulate and overdose can lead to fatal bleeding. Improving the dose regulation requires understanding how VKAs inhibit VKOR, which is a membrane-embedded enzyme difficult to characterize with structural and biochemical studies. Here we achieve a long-standing goal of obtaining crystal structures of human VKOR with warfarin, which represents coumarin-based VKAs; with phenindione, which represents indandione-based VKAs; with superwarfarins, the most commonly used rodenticides; and with vitamin K epoxide in a reaction intermediate state. We have also solved structures of a VKOR-like homolog with warfarin, with vitamin K substrates, and without ligand. These structures show that human VKOR adopts an overall fold with four transmembrane helices (TM) and a large ER-luminal region. VKAs are bound at the active site of HsVKOR, which is formed by the surrounding four-TM bundle and a cap domain on top. The cap domain is stabilized by a linked anchor domain that interacts with the membrane surface. VKOR binds specifically to VKAs through hydrogen bonding to their diketone groups. Mutating VKOR residues recognizing the diketones render strong warfarin resistance. Except the hydrogen bonds, the binding pocket is largely hydrophobic. This pocket is incompatible with warfarin metabolite, explaining the inactivation of warfarin through CYP2C9 metabolism; CYP2C9 and VKOR genotypes can explain 30-50% of the patient variability in warfarin dose. In addition, the high potency of superwarfarins is due to the interaction of their side group with a tunnel where the isoprenyl chain of vitamin K is bound. For VKOR catalysis, the same residues affording the VKA-binding specificity also facilitate substrate reduction Initiation of the catalysis requires a reactive cysteine to form a substrate adduct. Interactions from this stably bound adduct induces a closed conformation, thereby triggering electron transfer to reduce the substrate. Importantly, the open to closed conformational change during catalysis similar to that induced by the binding of VKAs. Taken together, VKAs achieve inhibition through mimicking key interactions and conformational changes required for VKOR catalytic cycle. Understanding of these mechanisms will enable improved strategy to regulate warfarin dose and have a broad impact on thromboembolic diseases and bone disorders. Disclosures No relevant conflicts of interest to declare.

scholarly journals Molecular evolution of the switch for progesterone and spironolactone from mineralocorticoid receptor agonist to antagonist

2019 ◽  
Vol 116 (37) ◽  
pp. 18578-18583 ◽  
Author(s):  
Peter J. Fuller ◽  
Yi-Zhou Yao ◽  
Ruitao Jin ◽  
Sitong He ◽  
Beatriz Martín-Fernández ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Conformational Changes ◽  
Mineralocorticoid Receptor ◽  
Steroid Receptors ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Site Directed Mutagenesis ◽  
Structural Basis ◽  
Terrestrial Vertebrates ◽  
Terrestrial Vertebrate

The mineralocorticoid receptor (MR) is highly conserved across vertebrate evolution. In terrestrial vertebrates, the MR mediates sodium homeostasis by aldosterone and also acts as a receptor for cortisol. Although the MR is present in fish, they lack aldosterone. The MR binds progesterone and spironolactone as antagonists in human MR but as agonists in zebrafish MR. We have defined the molecular basis of these divergent responses using MR chimeras between the zebrafish and human MR coupled with reciprocal site-directed mutagenesis and molecular dynamic (MD) simulation based on the crystal structures of the MR ligand-binding domain. Substitution of a leucine by threonine in helix 8 of the ligand-binding domain of the zebrafish MR confers the antagonist response. This leucine is conserved across fish species, whereas threonine (serine in rodents) is conserved in terrestrial vertebrate MR. MD identified an interaction of the leucine in helix 8 with a highly conserved leucine in helix 1 that stabilizes the agonist conformation including the interaction between helices 3 and 5, an interaction which has previously been characterized. This switch in the MR coincides with the evolution of terrestrial vertebrates and of aldosterone synthesis. It was perhaps mandatory if the appearance of aldosterone as a specific mediator of the homeostatic salt retention was to be tolerated. The conformational changes also provide insights into the structural basis of agonism versus antagonism in steroid receptors with potential implications for drug design in this important therapeutic target.

scholarly journals Rhodopsin: Structural Basis of Molecular Physiology

2001 ◽  
Vol 81 (4) ◽  
pp. 1659-1688 ◽  
Author(s):  
Santosh T. Menon ◽  
May Han ◽  
Thomas P. Sakmar
Keyword(s):  
Ligand Binding ◽  
Conformational Changes ◽  
Critical Evaluation ◽  
Binding Pocket ◽  
Receptor Activation ◽  
Structural Basis ◽  
Molecular Physiology ◽  
Movement Model ◽  
Ligand Binding Pocket ◽  
Cytoplasmic Surface

The crystal structure of rod cell visual pigment rhodopsin was recently solved at 2.8-Å resolution. A critical evaluation of a decade of structure-function studies is now possible. It is also possible to begin to explain the structural basis for several unique physiological properties of the vertebrate visual system, including extremely low dark noise levels as well as high gain and color detection. The ligand-binding pocket of rhodopsin is remarkably compact, and several apparent chromophore-protein interactions were not predicted from extensive mutagenesis or spectroscopic studies. The transmembrane helices are interrupted or kinked at multiple sites. An extensive network of interhelical interactions stabilizes the ground state of the receptor. The helix movement model of receptor activation, which might apply to all G protein-coupled receptors (GPCRs) of the rhodopsin family, is supported by several structural elements that suggest how light-induced conformational changes in the ligand-binding pocket are transmitted to the cytoplasmic surface. The cytoplasmic domain of the receptor is remarkable for a carboxy-terminal helical domain extending from the seventh transmembrane segment parallel to the bilayer surface. Thus the cytoplasmic surface appears to be approximately the right size to bind to the transducin heterotrimer in a one-to-one complex. Future high-resolution structural studies of rhodopsin and other GPCRs will form a basis to elucidate the detailed molecular mechanism of GPCR-mediated signal transduction.

scholarly journals Kinetic and Thermodynamic Characterization of Dihydrotestosterone-Induced Conformational Perturbations in Androgen Receptor Ligand-Binding Domain

2009 ◽  
Vol 23 (8) ◽  
pp. 1231-1241 ◽  
Author(s):  
Ravi Jasuja ◽  
Jagadish Ulloor ◽  
Christopher M. Yengo ◽  
Karen Choong ◽  
Andrei Y. Istomin ◽  
...  
Keyword(s):  
Androgen Receptor ◽  
Ligand Binding ◽  
Conformational Changes ◽  
Solvent Accessibility ◽  
Molten Globule ◽  
Binding Pocket ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Second Derivative ◽  
Ligand Binding Pocket

Abstract Ligand-induced conformational perturbations in androgen receptor (AR) are important in coactivator recruitment and transactivation. However, molecular rearrangements in AR ligand-binding domain (AR-LBD) associated with agonist binding and their kinetic and thermodynamic parameters are poorly understood. We used steady-state second-derivative absorption and emission spectroscopy, pressure and temperature perturbations, and 4,4′-bis-anilinonaphthalene 8-sulfonate (bis-ANS) partitioning to determine the kinetics and thermodynamics of the conformational changes in AR-LBD after dihydrotestosterone (DHT) binding. In presence of DHT, the second-derivative absorption spectrum showed a red shift and a change in peak-to-peak distance. Emission intensity increased upon DHT binding, and center of spectral mass was blue shifted, denoting conformational changes resulting in more hydrophobic environment for tyrosines and tryptophans within a more compact DHT-bound receptor. In pressure perturbation calorimetry, DHT-induced energetic stabilization increased the Gibbs free energy of unfolding to 8.4 ± 1.3 kcal/mol from 3.5 ± 1.6 kcal/mol. Bis-ANS partitioning studies revealed that upon DHT binding, AR-LBD underwent biphasic rearrangement with a high activation energy (13.4 kcal/mol). An initial, molten globule-like burst phase (k ∼30 sec−1) with greater solvent accessibility was followed by rearrangement (k ∼0.01 sec−1), leading to a more compact conformation than apo-AR-LBD. Molecular simulations demonstrated unique sensitivity of tyrosine and tryptophan residues during pressure unfolding with rearrangement of residues in the coactivator recruitment surfaces distant from the ligand-binding pocket. In conclusion, DHT binding leads to energetic stabilization of AR-LBD domain and substantial rearrangement of residues distant from the ligand-binding pocket. DHT binding to AR-LBD involves biphasic receptor rearrangement including population of a molten globule-like intermediate state.

scholarly journals The flexible N-terminus of BchL autoinhibits activity through interaction with its [4Fe-4S] cluster and relieved upon ATP binding

2020 ◽  
pp. jbc.RA120.016278
Author(s):  
Elliot I Corless ◽  
Syed Muhammad Saad Imran ◽  
Maxwell B Watkins ◽  
John-Paul Bacik ◽  
Jenna Mattice ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Local Environment ◽  
Binding Pocket ◽  
Free Form ◽  
Atp Binding ◽  
Atp Binding Site ◽  
Exchange Mass Spectrometry ◽  
Protochlorophyllide Reduction ◽  
N Terminus ◽  
Poor Tolerance

A key step in bacteriochlorophyll biosynthesis is the reduction of protochlorophyllide to chlorophyllide, catalyzed by dark-operative protochlorophyllide oxidoreductase (DPOR). DPOR contains two [4Fe-4S]-containing component proteins (BchL and BchNB) that assemble upon ATP binding to BchL to coordinate electron transfer and protochlorophyllide reduction. But the precise nature of the ATP-induced conformational changes are poorly understood. We present a crystal structure of BchL in the nucleotide-free form where a conserved, flexible region in the N-terminus masks the [4Fe-4S] cluster at the docking interface between BchL and BchNB. Amino acid substitutions in this region produce a hyper-active enzyme complex, suggesting a role for the N-terminus in auto-inhibition. Hydrogen deuterium exchange mass spectrometry shows that ATP-binding to BchL produces specific conformational changes leading to release of the flexible N-terminus from the docking interface. The release also promotes changes within the local environment surrounding the [4Fe-4S] cluster and promotes BchL complex formation with BchNB. A key patch of amino acids, Asp-Phe-Asp (the ‘DFD patch’), situated at the mouth of the BchL ATP-binding pocket promotes inter-subunit cross stabilization of the two subunits. A linked BchL dimer with one defective ATP-binding site does not support protochlorophyllide reduction, illustrating nucleotide binding to both subunits as a prerequisite for the inter-subunit cross stabilization. The masking of the [4Fe-4S] cluster by the flexible N-terminal region and the associated inhibition of activity is a novel mechanism of regulation in metalloproteins. Such mechanisms are possibly an adaptation to the anaerobic nature of eubacterial cells with poor tolerance for oxygen.

scholarly journals Characterization of the nucleotide-binding domain NsrF from the BceAB-type ABC-transporter NsrFP from the human pathogen Streptococcus agalactiae

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Fabia Furtmann ◽  
Nicola Porta ◽  
Dai Tri Hoang ◽  
Jens Reiners ◽  
Julia Schumacher ◽  
...  
Keyword(s):  
Streptococcus Agalactiae ◽  
Bacterial Infections ◽  
Nucleotide Binding ◽  
Resistance Mechanisms ◽  
Binding Domain ◽  
Binding Modes ◽  
Human Pathogens ◽  
Nucleotide Binding Domain ◽  
Transporter Family

Abstract Treatment of bacterial infections is a great challenge of our era due to the various resistance mechanisms against antibiotics. Antimicrobial peptides are considered to be potential novel compound as antibiotic treatment. However, some bacteria, especially many human pathogens, are inherently resistant to these compounds, due to the expression of BceAB-type ABC transporters. This rather new transporter family is not very well studied. Here, we report the first full characterization of the nucleotide binding domain of a BceAB type transporter from Streptococcus agalactiae, namely SaNsrF of the transporter SaNsrFP, which confers resistance against nisin and gallidermin. We determined the NTP hydrolysis kinetics and used molecular modeling and simulations in combination with small angle X-ray scattering to obtain structural models of the SaNsrF monomer and dimer. The fact that the SaNsrFH202A variant displayed no ATPase activity was rationalized in terms of changes of the structural dynamics of the dimeric interface. Kinetic data show a clear preference for ATP as a substrate, and the prediction of binding modes allowed us to explain this selectivity over other NTPs.

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