scholarly journals Active site plasticity and possible modes of chemical inhibition of the human DNA deaminase APOBEC3B

2019 ◽  
Author(s):  
Ke Shi ◽  
Özlem Demir ◽  
Michael A. Carpenter ◽  
Surajit Banerjee ◽  
Daniel A. Harki ◽  
...  
Keyword(s):  
Small Molecules ◽  
Small Molecule ◽  
Active Site ◽  
Rational Design ◽  
Catalytic Domain ◽  
Critical Role ◽  
Cytosine Deaminase ◽  
Zinc Ion ◽  
Tumor Evolution ◽  
Active Site Residues

AbstractThe single-stranded DNA cytosine deaminase APOBEC3B (A3B) functions in innate immunity against viruses, but is also strongly implicated in eliciting mutations in cancer genomes. Because of the critical role of A3B in promoting virus and tumor evolution, small molecule inhibitors are desirable. However, there is no reported structure for any of the APOBEC3-family enzymes in complex with a small molecule bound in the active site, which hampers the development of small molecules targeting A3B. Here we report high-resolution structures of an active A3B catalytic domain chimera with loop 7 residues exchanged with those from the corresponding region of APOBEC3G (A3G). The structures reveal novel open conformations lacking the catalytically essential zinc ion, with the highly conserved active site residues extensively rearranged. These inactive conformations are stabilized by 2-pyrimidone or an iodide ion bound in the active site. Molecular dynamics simulations corroborate the remarkable plasticity of the engineered active site and identify key interactions that stabilize the native A3B active site. These data provide insights into A3B active site dynamics and suggest possible modes of its inhibition by small molecules, which would aid in rational design of selective A3B inhibitors for constraining virus and tumor evolution.

scholarly journals STEM-20. A CANCER STEM CELL-SELECTIVE APOPTOSIS-INDUCING SMALL MOLECULE FOR THE TREATMENT OF GBM

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii200-ii200
Author(s):  
Stephen Skirboll ◽  
Natasha Lucki ◽  
Genaro Villa ◽  
Naja Vergani ◽  
Michael Bollong ◽  
...  
Keyword(s):  
Stem Cells ◽  
Cancer Stem Cells ◽  
Small Molecules ◽  
Small Molecule ◽  
Large Scale ◽  
Critical Role ◽  
Tumor Formation ◽  
Cell Type ◽  
Caspase 1 ◽  
Activation Assay

Abstract INTRODUCTION Glioblastoma multiforme (GBM) is the most aggressive form of primary brain cancer. A subpopulation of multipotent cells termed GBM cancer stem cells (CSCs) play a critical role in tumor initiation and maintenance, drug resistance, and recurrence following surgery. New therapeutic strategies for the treatment of GBM have recently focused on targeting CSCs. Here we have used an unbiased large-scale screening approach to identify drug-like small molecules that induce apoptosis in GBM CSCs in a cell type-selective manner. METHODS A luciferase-based survival assay of patient-derived GBM CSC lines was established to perform a large-scale screen of ∼one million drug-like small molecules with the goal of identifying novel compounds that are selectively toxic to chemoresistant GBM CSCs. Compounds found to kill GBM CSC lines as compared to control cell types were further characterized. A caspase activation assay was used to evaluate the mechanism of induced cell death. A xenograft animal model using patient-derived GBM CSCs was employed to test the leading candidate for suppression of in vivo tumor formation. RESULTS We identified a small molecule, termed RIPGBM, from the cell-based chemical screen that induces apoptosis in primary patient-derived GBM CSC cultures. The cell type-dependent selectivity of RIPGBM appears to arise at least in part from redox-dependent formation of a proapoptotic derivative, termed cRIPGBM, in GBM CSCs. cRIPGBM induces caspase 1-dependent apoptosis by binding to receptor-interacting protein kinase 2 (RIPK2) and acting as a molecular switch, which reduces the formation of a prosurvival RIPK2/TAK1 complex and increases the formation of a proapoptotic RIPK2/caspase 1 complex. In an intracranial GBM xenograft mouse model, RIPGBM was found to significantly suppress tumor formation. CONCLUSIONS Our chemical genetics-based approach has identified a small molecule drug candidate and a potential drug target that selectively targets cancer stem cells and provides an approach for the treatment of GBMs.

scholarly journals A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

2016 ◽  
Vol 12 ◽  
pp. 125-138 ◽  
Author(s):  
Steven C Zimmerman
Keyword(s):  
Small Molecules ◽  
Supramolecular Chemistry ◽  
Myotonic Dystrophy ◽  
Small Molecule ◽  
Early Life ◽  
Rational Design ◽  
Early Experience ◽  
Therapeutic Agents ◽  
Early Career ◽  
Molecular Tweezers

This review summarizes part of the author’s research in the area of supramolecular chemistry, beginning with his early life influences and early career efforts in molecular recognition, especially molecular tweezers. Although designed to complex DNA, these hosts proved more applicable to the field of host–guest chemistry. This early experience and interest in intercalation ultimately led to the current efforts to develop small molecule therapeutic agents for myotonic dystrophy using a rational design approach that heavily relies on principles of supramolecular chemistry. How this work was influenced by that of others in the field and the evolution of each area of research is highlighted with selected examples.

scholarly journals Biological and Structural Characterization of Trypanosoma cruzi Phosphodiesterase C and Implications for Design of Parasite Selective Inhibitors

2012 ◽  
Vol 287 (15) ◽  
pp. 11788-11797 ◽  
Author(s):  
Huanchen Wang ◽  
Stefan Kunz ◽  
Gong Chen ◽  
Thomas Seebeck ◽  
Yiqian Wan ◽  
...  
Keyword(s):  
Trypanosoma Cruzi ◽  
Crystal Structures ◽  
Active Site ◽  
Catalytic Domain ◽  
Trypanosoma Evansi ◽  
Active Site Residues ◽  
Dual Specificity ◽  
Pde Inhibitors ◽  
Starting Model

Trypanosoma cruzi phosphodiesterase C (TcrPDEC) is a potential new drug target for the treatment of Chagas disease but has not been well studied. This study reports the enzymatic properties of various kinetoplastid PDECs and the crystal structures of the unliganded TcrPDEC1 catalytic domain and its complex with an inhibitor. Mutations of PDEC during the course of evolution led to inactivation of PDEC in Trypanosoma brucei/Trypanosoma evansi/Trypanosoma congolense, whereas the enzyme is active in all other kinetoplastids. The TcrPDEC1 catalytic domain hydrolyzes both cAMP and cGMP with a Km of 23.8 μm and a kcat of 31 s−1 for cAMP and a Km of 99.1 μm and a kcat of 17 s−1 for cGMP, thus confirming its dual specificity. The crystal structures show that the N-terminal fragment wraps around the TcrPDEC catalytic domain and may thus regulate its enzymatic activity via direct interactions with the active site residues. A PDE5 selective inhibitor that has an IC50 of 230 nm for TcrPDEC1 binds to TcrPDEC1 in an orientation opposite to that of sildenafil. This observation, together with the screen of the inhibitory potency of human PDE inhibitors against TcrPDEC, implies that the scaffold of some human PDE inhibitors might be used as the starting model for design of parasite PDE inhibitors. The structural study also identified a unique parasite pocket that neighbors the active site and may thus be valuable for the design of parasite-specific inhibitors.

scholarly journals Identification of a ligand binding hot spot and structural motifs replicating aspects of tyrosyl-DNA phosphodiesterase I (TDP1) phosphoryl recognition by crystallographic fragment cocktail screening

2019 ◽  
Vol 47 (19) ◽  
pp. 10134-10150 ◽  
Author(s):  
George T Lountos ◽  
Xue Zhi Zhao ◽  
Evgeny Kiselev ◽  
Joseph E Tropea ◽  
Danielle Needle ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Small Molecule ◽  
Anticancer Agents ◽  
Active Site ◽  
Catalytic Domain ◽  
Hot Spot ◽  
Alkylating Agents ◽  
Fragment Screening ◽  
Rational Development ◽  
Biochemical Assays

Abstract Tyrosyl DNA-phosphodiesterase I (TDP1) repairs type IB topoisomerase (TOP1) cleavage complexes generated by TOP1 inhibitors commonly used as anticancer agents. TDP1 also removes DNA 3′ end blocking lesions generated by chain-terminating nucleosides and alkylating agents, and base oxidation both in the nuclear and mitochondrial genomes. Combination therapy with TDP1 inhibitors is proposed to synergize with topoisomerase targeting drugs to enhance selectivity against cancer cells exhibiting deficiencies in parallel DNA repair pathways. A crystallographic fragment screening campaign against the catalytic domain of TDP1 was conducted to identify new lead compounds. Crystal structures revealed two fragments that bind to the TDP1 active site and exhibit inhibitory activity against TDP1. These fragments occupy a similar position in the TDP1 active site as seen in prior crystal structures of TDP1 with bound vanadate, a transition state mimic. Using structural insights into fragment binding, several fragment derivatives have been prepared and evaluated in biochemical assays. These results demonstrate that fragment-based methods can be a highly feasible approach toward the discovery of small-molecule chemical scaffolds to target TDP1, and for the first time, we provide co-crystal structures of small molecule inhibitors bound to TDP1, which could serve for the rational development of medicinal TDP1 inhibitors.

scholarly journals A Critical Role of Non-active Site Residues on Cyclooxygenase Helices 5 and 6 in the Control of Prostaglandin Stereochemistry at Carbon 15

2007 ◽  
Vol 282 (38) ◽  
pp. 28157-28163 ◽  
Author(s):  
Karin Valmsen ◽  
William E. Boeglin ◽  
Reet Järving ◽  
Ivar Järving ◽  
Külliki Varvas ◽  
...  
Keyword(s):  
Amino Acid ◽  
Active Site ◽  
Amino Acid Sequence Identity ◽  
Critical Role ◽  
Site Directed Mutagenesis ◽  
Single Amino Acid ◽  
Active Site Residues ◽  
The Core ◽  
The Difference

The correct stereochemistry of prostaglandins is a prerequisite of their biological activity and thus is under a strict enzymatic control. Recently, we cloned and characterized two cyclooxygenase (COX) isoforms in the coral Plexaura homomalla that share 97% amino acid sequence identity, yet form prostaglandins with opposite stereochemistry at carbon 15. The difference in oxygenation specificity is only partially accounted for by the single amino acid substitution in the active site (Ile or Val at position 349). For further elucidation of residues involved in the C-15 stereocontrol, a series of sequence swapping and site-directed mutagenesis experiments between 15R- and 15S-COX were performed. Our results show that the change in stereochemistry at carbon 15 of prostaglandins relates mainly to five amino acid substitutions on helices 5 and 6 of the coral COX. In COX proteins, these helices form a helix-turn-helix motif that traverses through the entire protein, contributing to the second shell of residues around the oxygenase active site; it constitutes the most highly conserved region where even slight changes result in loss of catalytic activity. The finding that this region is among the least conserved between the P. homomalla 15S- and 15R-specific COX further supports its significance in maintaining the desired prostaglandin stereochemistry at C-15. The results are particularly remarkable because, based on its strong conservation, the conserved middle of helix 5 is considered as central to the core structure of peroxidases, of which COX proteins are derivatives. Now we show that the same parts of the protein are involved in the control of oxygenation with 15R or 15S stereospecificity in the dioxygenase active site.

scholarly journals The catalytic domain of avian sarcoma virus integrase: conformation of the active-site residues in the presence of divalent cations

Structure ◽  
1996 ◽  
Vol 4 (1) ◽  
pp. 89-96 ◽  
Author(s):  
Grzegorz Bujacz ◽  
Mariusz Jaskólski ◽  
Jerry Alexandratos ◽  
Alexander Wlodawer ◽  
George Merkel ◽  
...  
Keyword(s):  
Active Site ◽  
Catalytic Domain ◽  
Divalent Cations ◽  
Avian Sarcoma Virus ◽  
Active Site Residues ◽  
Sarcoma Virus ◽  
Avian Sarcoma

scholarly journals Design of a small molecule against an oncogenic noncoding RNA

2016 ◽  
Vol 113 (21) ◽  
pp. 5898-5903 ◽  
Author(s):  
Sai Pradeep Velagapudi ◽  
Michael D. Cameron ◽  
Christopher L. Haga ◽  
Laura H. Rosenberg ◽  
Marie Lafitte ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Small Molecules ◽  
Cancer Cells ◽  
Small Molecule ◽  
Noncoding Rna ◽  
Breast Cancer Cells ◽  
Rational Design ◽  
Pharmacokinetic Profile ◽  
Tumor Burden

The design of precision, preclinical therapeutics from sequence is difficult, but advances in this area, particularly those focused on rational design, could quickly transform the sequence of disease-causing gene products into lead modalities. Herein, we describe the use of Inforna, a computational approach that enables the rational design of small molecules targeting RNA to quickly provide a potent modulator of oncogenic microRNA-96 (miR-96). We mined the secondary structure of primary microRNA-96 (pri-miR-96) hairpin precursor against a database of RNA motif–small molecule interactions, which identified modules that bound RNA motifs nearby and in the Drosha processing site. Precise linking of these modules together provided Targaprimir-96 (3), which selectively modulates miR-96 production in cancer cells and triggers apoptosis. Importantly, the compound is ineffective on healthy breast cells, and exogenous overexpression of pri-miR-96 reduced compound potency in breast cancer cells. Chemical Cross-Linking and Isolation by Pull-Down (Chem-CLIP), a small-molecule RNA target validation approach, shows that 3 directly engages pri-miR-96 in breast cancer cells. In vivo, 3 has a favorable pharmacokinetic profile and decreases tumor burden in a mouse model of triple-negative breast cancer. Thus, rational design can quickly produce precision, in vivo bioactive lead small molecules against hard-to-treat cancers by targeting oncogenic noncoding RNAs, advancing a disease-to-gene-to-drug paradigm.

The outcomes of small-molecule kinase inhibitors and the role of ROCK2 as a molecular target for the treatment of Alzheimer's disease

2021 ◽  
Vol 20 ◽  
Author(s):  
Heber Victor Tolomeu ◽  
Carlos Alberto Manssour Fraga
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Small Molecule ◽  
Active Site ◽  
Rational Design ◽  
Kinase Inhibitors ◽  
Structural Characteristics ◽  
Structural Features ◽  
Relationship Analysis ◽  
Promising Target

Background: Alzheimer's disease is rapidly becoming a major threat to public health, with an increasing number of individuals affected as the world's population ages. In this sense, studies have been carried out aiming at the identification of new small-molecule kinase inhibitors useful for the treatment of Alzheimer's disease. Objective: In the present study, we investigated the compounds developed as inhibitors of different protein kinases associated with the pathogenesis of Alzheimer's disease. Methods: The applied methodology was the use of the Clarivate Analytics Integrity and ClinicalTrials.com databases. Moreover, we highlight ROCK2 as a promising target despite being little studied for this purpose. A careful structure-activity relationship analysis of the ROCK2 inhibitors was performed to identify important structural features and fragments for the interaction with the kinase active site, aiming to rationally design novel potent and selective inhibitors. Results: We were able to notice some structural characteristics that could serve as the basis to better guide the rational design of new ROCK2 inhibitors as well as some more in-depth characteristics regarding the topology of the active site of both isoforms of these enzymes, thereby identifying differences that could lead to planning more selective compounds. Conclusion: We hope that this work can be useful to update researchers working in this area, enabling the emergence of new ideas and a greater direction of efforts for designing new ROCK2 inhibitors to identify new therapeutic alternatives for Alzheimer's disease.

scholarly journals Structural modelling and mutagenesis of human cytomegalovirus alkaline nuclease UL98

2012 ◽  
Vol 93 (1) ◽  
pp. 130-138 ◽  
Author(s):  
Alison L. Kuchta ◽  
Hardik Parikh ◽  
Yali Zhu ◽  
Glen E. Kellogg ◽  
Deborah S. Parris ◽  
...  
Keyword(s):  
Viral Replication ◽  
Human Cytomegalovirus ◽  
Active Site ◽  
Rational Design ◽  
Structural Modelling ◽  
Active Site Residues ◽  
Amino Terminal ◽  
Alkaline Nuclease ◽  
Dna Substrate ◽  
Active Site Region

Human cytomegalovirus encodes an alkaline nuclease, UL98, that is highly conserved among herpesviruses and has both endonuclease (endo) and exonuclease (exo) activities. This protein is thought to be important for viral replication and therefore represents a potential target for antiviral development; however, little is known about its structure or role in viral replication. Comparative structural modelling was used to build a model of UL98 based on the known structure of shutoff and exonuclease protein from Kaposi’s sarcoma-associated herpesvirus. The model predicts that UL98 residues D254, E278 and K280 represent the critical aspartic acid, glutamic acid and lysine active-site residues, respectively, while R164 and S252 correspond to residues proposed to bind the 5′ phosphate of the DNA substrate. UL98 with an amino-terminal hexahistidine tag was expressed in Escherichia coli, purified by affinity chromatography and confirmed to have exo and endo activities. Amino acid substitutions D254A, E278A, K280A and S252A virtually eliminated exo and endo activities, whereas R164A retained full endo activity but only 10 % of the exo activity compared with the wild-type enzyme. A mutant virus lacking UL98 was viable but severely attenuated for replication, while one expressing UL98(R164A) replicated normally. These results confirm the utility of the model in representing the active-site region of UL98 and suggest a mechanism for the differentiation of endonuclease and exonuclease activities. These findings could facilitate the exploration of the roles of alkaline nucleases in herpesvirus replication and the rational design of inhibitors that target their enzymic activities.

scholarly journals Tuning the Specificity of the Recombinant Multicomponent Tolueneo-Xylene Monooxygenase from Pseudomonas sp. Strain OX1 for the Biosynthesis of Tyrosol from 2-Phenylethanol

2011 ◽  
Vol 77 (15) ◽  
pp. 5428-5437 ◽  
Author(s):  
Eugenio Notomista ◽  
Roberta Scognamiglio ◽  
Luca Troncone ◽  
Giuliana Donadio ◽  
Alessandro Pezzella ◽  
...  
Keyword(s):  
Active Site ◽  
Rational Design ◽  
Wide Spectrum ◽  
Wild Type ◽  
Active Site Residues ◽  
Primary Interest ◽  
Content Type ◽  
Commercial Scale ◽  
Recombinant Cells ◽  
Molecular Determinants

ABSTRACTBiocatalysis is today a standard technology for the industrial production of several chemicals, and the number of biotransformation processes running on a commercial scale is constantly increasing. Among biocatalysts, bacterial multicomponent monooxygenases (BMMs), a diverse group of nonheme diiron enzymes that activate dioxygen, are of primary interest due to their ability to catalyze a variety of complex oxidations, including reactions of mono- and dihydroxylation of phenolic compounds. In recent years, both directed evolution and rational design have been successfully used to identify the molecular determinants responsible for BMM regioselectivity and to improve their activity toward natural and nonnatural substrates. Tolueneo-xylene monooxygenase (ToMO) is a BMM isolated fromPseudomonassp. strain OX1 which hydroxylates a wide spectrum of aromatic compounds. In this work we investigate the use of recombinant ToMO for the biosynthesis in recombinant cells ofEscherichia colistrain JM109 of 4-hydroxyphenylethanol (tyrosol), an antioxidant present in olive oil, from 2-phenylethanol, a cheap and commercially available substrate. We initially found that wild-type ToMO is unable to convert 2-phenylethanol to tyrosol. This was explained by using a computational model which analyzed the interactions between ToMO active-site residues and the substrate. We found that residue F176 is the major steric hindrance for the correct positioning of the reaction intermediate leading to tyrosol production into the active site of the enzyme. Several mutants were designed and prepared, and we found that the combination of different mutations at position F176 with mutation E103G allows ToMO to convert up to 50% of 2-phenylethanol into tyrosol in 2 h.

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