1
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Ramachandran V, Potoyan DA. Energy landscapes of homopolymeric RNAs revealed by deep unsupervised learning. Biophys J 2024; 123:1152-1163. [PMID: 38571310 PMCID: PMC11079944 DOI: 10.1016/j.bpj.2024.04.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 03/03/2024] [Accepted: 04/01/2024] [Indexed: 04/05/2024] Open
Abstract
Conformational dynamics of RNA plays important roles in a variety of cellular functions such as transcriptional regulation, catalysis, scaffolding, and sensing. Recently, RNAs with low-complexity sequences have been shown to phase separate and form condensate phases similar to lowcomplexity protein domains. The affinity for phase separation and the material characteristics of RNA condensates are strongly dependent on sequence composition and patterning. We hypothesize that differences in the affinities for RNA phase separation can be uncovered by studying sequence-dependent conformational dynamics of single RNA chains. To this end, we have employed atomistic simulations and deep dimensionality reduction techniques to map temperature-dependent conformational free energy landscapes for 20 base-long homopolymeric RNA sequences: poly(U), poly(G), poly(C), and poly(A). The energy landscapes of homopolymeric RNAs reveal a plethora of metastable states with qualitatively different populations stemming from differences in base chemistry. Through detailed analysis of base, phosphate, and sugar interactions, we show that experimentally observed temperature-driven shifts in metastable state populations align with experiments on RNA phase transitions. Specifically, we find that the thermodynamics of unfolding of homopolymeric RNA follows the poly(G) > poly(A) > poly(C) > poly(U) order of stability, mirroring the propensity of RNA to form condensates. To conclude, this work shows that at least for homopolymeric RNA sequences the single-chain conformational dynamics contains sufficient information for predicting and quantifying condensate forming affinities of RNAs. Thus, we anticipate that atomically detailed studies of temeprature -dependent energy landscapes of RNAs will be a useful guide for understanding the propensity of various RNA molecules to form condensates.
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Affiliation(s)
| | - Davit A Potoyan
- Department of Chemistry, Iowa State University, Ames, Iowa; Department of Biochemistry Biophysics and Molecular Biology, Iowa State University, Ames, Iowa.
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2
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Basu S, Gohain N, Kim J, Trinh HV, Choe M, Joyce MG, Rao M. Determination of Binding Affinity of Antibodies to HIV-1 Recombinant Envelope Glycoproteins, Pseudoviruses, Infectious Molecular Clones, and Cell-Expressed Trimeric gp160 Using Microscale Thermophoresis. Cells 2023; 13:33. [PMID: 38201237 PMCID: PMC10778174 DOI: 10.3390/cells13010033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 11/27/2023] [Accepted: 12/13/2023] [Indexed: 01/12/2024] Open
Abstract
Developing a preventative vaccine for HIV-1 has been a global priority. The elicitation of broadly neutralizing antibodies (bNAbs) against a broad range of HIV-1 envelopes (Envs) from various strains appears to be a critical requirement for an efficacious HIV-1 vaccine. To understand their ability to neutralize HIV-1, it is important to characterize the binding characteristics of bNAbs. Our work is the first to utilize microscale thermophoresis (MST), a rapid, economical, and flexible in-solution temperature gradient method to quantitatively determine the binding affinities of bNAbs and non-neutralizing monoclonal antibodies (mAbs) to HIV-1 recombinant envelope monomer and trimer proteins of different subtypes, pseudoviruses (PVs), infectious molecular clones (IMCs), and cells expressing the trimer. Our results demonstrate that the binding affinities were subtype-dependent. The bNAbs exhibited a higher affinity to IMCs compared to PVs and recombinant proteins. The bNAbs and mAbs bound with high affinity to native-like gp160 trimers expressed on the surface of CEM cells compared to soluble recombinant proteins. Interesting differences were seen with V2-specific mAbs. Although they recognize linear epitopes, one of the antibodies also bound to the Envs on PVs, IMCs, and a recombinant trimer protein, suggesting that the epitope was not occluded. The identification of epitopes on the envelope surface that can bind to high affinity mAbs could be useful for designing HIV-1 vaccines and for down-selecting vaccine candidates that can induce high affinity antibodies to the HIV-1 envelope in their native conformation.
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Affiliation(s)
- Shraddha Basu
- Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD 20817, USA; (S.B.); (N.G.); (J.K.); (H.V.T.); (M.C.); (M.G.J.)
- US Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA
| | - Neelakshi Gohain
- Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD 20817, USA; (S.B.); (N.G.); (J.K.); (H.V.T.); (M.C.); (M.G.J.)
- US Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA
| | - Jiae Kim
- Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD 20817, USA; (S.B.); (N.G.); (J.K.); (H.V.T.); (M.C.); (M.G.J.)
- US Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA
| | - Hung V. Trinh
- Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD 20817, USA; (S.B.); (N.G.); (J.K.); (H.V.T.); (M.C.); (M.G.J.)
- US Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA
| | - Misook Choe
- Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD 20817, USA; (S.B.); (N.G.); (J.K.); (H.V.T.); (M.C.); (M.G.J.)
- Emerging Infectious Disease Branch, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA
| | - M. Gordon Joyce
- Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD 20817, USA; (S.B.); (N.G.); (J.K.); (H.V.T.); (M.C.); (M.G.J.)
- Emerging Infectious Disease Branch, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA
| | - Mangala Rao
- US Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA
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3
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Shino A, Otsu M, Imai K, Fukuzawa K, Morishita EC. Probing RNA-Small Molecule Interactions Using Biophysical and Computational Approaches. ACS Chem Biol 2023; 18:2368-2376. [PMID: 37856793 PMCID: PMC10662358 DOI: 10.1021/acschembio.3c00287] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 08/30/2023] [Indexed: 10/21/2023]
Abstract
Interest in small molecules that target RNA is flourishing, and the expectation set on them to treat diseases with unmet medical needs is high. However, several challenges remain, including difficulties in selecting suitable tools and establishing workflows for their discovery. In this context, we optimized experimental and computational approaches that were previously employed for the protein targets. Here, we demonstrate that a fluorescence-based assay can be effectively used to screen small molecule libraries for their ability to bind and stabilize an RNA stem-loop. Our screen identified several fluoroquinolones that bind to the target stem-loop. We further probed their interactions with the target using biolayer interferometry, isothermal titration calorimetry (ITC), and nuclear magnetic resonance spectroscopy. The results of these biophysical assays suggest that the fluoroquinolones bind the target in a similar manner. Armed with this knowledge, we built models for the complexes of the fluoroquinolones and the RNA target. Then, we performed fragment molecular orbital (FMO) calculations to dissect the interactions between the fluoroquinolones and the RNA. We found that the binding free energies obtained from the ITC experiments correlated strongly with the interaction energies calculated by FMO. Finally, we designed fluoroquinolone analogues and performed FMO calculations to predict their binding free energies. Taken together, the results of this study support the importance of conducting orthogonal assays in binding confirmation and compound selection and demonstrate the usefulness of FMO calculations in the rational design of RNA-targeted small molecules.
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Affiliation(s)
- Amiu Shino
- Basic
Research Division, Veritas In Silico Inc., Shinagawa, Tokyo 141-0031, Japan
| | - Maina Otsu
- Basic
Research Division, Veritas In Silico Inc., Shinagawa, Tokyo 141-0031, Japan
| | - Koji Imai
- Basic
Research Division, Veritas In Silico Inc., Shinagawa, Tokyo 141-0031, Japan
| | - Kaori Fukuzawa
- Graduate
School of Pharmaceutical Sciences, Osaka
University, Suita, Osaka 565-0871, Japan
- School
of Pharmacy and Pharmaceutical Sciences, Hoshi University, Shinagawa, Tokyo 142-8501, Japan
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4
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Thalhammer A, Bröker NK. Biophysical Approaches for the Characterization of Protein-Metabolite Interactions. Methods Mol Biol 2023; 2554:199-229. [PMID: 36178628 DOI: 10.1007/978-1-0716-2624-5_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
With an estimate of hundred thousands of protein molecules per cell and the number of metabolites several orders of magnitude higher, protein-metabolite interactions are omnipresent. In vitro analyses are one of the main pillars on the way to establish a solid understanding of how these interactions contribute to maintaining cellular homeostasis. A repertoire of biophysical techniques is available by which protein-metabolite interactions can be quantitatively characterized in terms of affinity, specificity, and kinetics in a broad variety of solution environments. Several of those provide information on local or global conformational changes of the protein partner in response to ligand binding. This review chapter gives an overview of the state-of-the-art biophysical toolbox for the study of protein-metabolite interactions. It briefly introduces basic principles, highlights recent examples from the literature, and pinpoints promising future directions.
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Affiliation(s)
- Anja Thalhammer
- Physical Biochemistry, University of Potsdam, Potsdam, Germany.
| | - Nina K Bröker
- Physical Biochemistry, University of Potsdam, Potsdam, Germany
- Health and Medical University Potsdam, Potsdam, Germany
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5
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Chramiec-Głąbik A, Rawski M, Glatt S, Lin TY. Electrophoretic Mobility Shift Assay (EMSA) and Microscale Thermophoresis (MST) Methods to Measure Interactions Between tRNAs and Their Modifying Enzymes. Methods Mol Biol 2023; 2666:29-53. [PMID: 37166655 DOI: 10.1007/978-1-0716-3191-1_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The Elongator complex is a unique tRNA acetyltransferase; it was initially annotated as a protein acetyltransferase, but in-depth biochemical analyses revealed its genuine function as a tRNA modifier. The substrate recognition and binding of the Elongator is mainly mediated by its catalytic Elp3 subunit. In this chapter, we describe protocols to generate fluorescently labeled RNAs and outline the principles underlying electrophoretic mobility shift assays (EMSA) and microscale thermophoresis (MST). These two methods allow qualitative and quantitative examinations of the binding affinity of various tRNAs toward the homologs of Elp3 from various organisms. The rather qualitative results from EMSA analyses can be nicely complemented by MST measurements allowing precise determination of the dissociation constant (KD). We also provide detailed notes for users to mitigate potential ambiguities and technical pitfalls during the procedures.
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Affiliation(s)
| | - Michał Rawski
- Malopolska Centre of Biotechnology (MCB), Jagiellonian University, Krakow, Poland
| | - Sebastian Glatt
- Malopolska Centre of Biotechnology (MCB), Jagiellonian University, Krakow, Poland.
| | - Ting-Yu Lin
- Malopolska Centre of Biotechnology (MCB), Jagiellonian University, Krakow, Poland.
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6
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Pandya N, Rani R, Kumar V, Kumar A. Discovery of potent Guanidine derivative that selectively binds and stabilizes the human BCL-2 G-quadruplex DNA and downregulates the transcription. Gene 2022; 851:146975. [PMID: 36261091 DOI: 10.1016/j.gene.2022.146975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 09/26/2022] [Accepted: 10/11/2022] [Indexed: 12/09/2022]
Abstract
Small molecules that interact with quadruplexes offer a wide range of potential applications, including not just as medications but also as sensors for quadruplexes structures. The BCL-2 is a proto-oncogene that often gets mutated in lethal cancer and could be an interesting target for developing an anti-cancer drug. In the present study, we have employed various biophysical techniques such as fluorescence, CD, Isothermal calorimeter, gel retardation, and PCR stop assay, indicating that Guanidine derivatives GD-1 and GD-2 selectively interact with high affinity with BCL-2 G-quadruplex over other G-quadruplex DNA and duplex DNA. The most promising small molecule GD-1 increases the thermostability of the BCL-2 GQ structure by 12°C. Our biological experiments such as ROS generation, qRT-PCR, western blot, TFP based Reporter assay, show that the GD-1 ligand causes a synthetic lethal interaction by suppressing the expression BCL-2 genes via interaction and stabilization of its the promoter G-quadruplexes in HeLa cells and act as a potential anti-cancer agent.
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Affiliation(s)
- Nirali Pandya
- Department for Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, Indore, Madhya Pradesh, 453552, Simrol, India
| | - Reshma Rani
- Department of Biotechnology, Amity University, Noida
| | - Vinit Kumar
- Amity Institute of Molecular Medicine and Stem Cell Research
| | - Amit Kumar
- Department for Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, Indore, Madhya Pradesh, 453552, Simrol, India.
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7
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Small Molecule Screening Discovers Compounds that Reduce FMRpolyG Protein Aggregates and Splicing Defect Toxicity in Fragile X-Associated Tremor/Ataxia Syndrome. Mol Neurobiol 2022; 59:1992-2007. [PMID: 35040038 DOI: 10.1007/s12035-021-02697-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 12/10/2021] [Indexed: 12/20/2022]
Abstract
Expansion of CGG trinucleotide repeats in 5' untranslated region of the FMR1 gene is the causative mutation of neurological diseases such as fragile X syndrome (FXS), fragile X-associated tremor/ataxia syndrome (FXTAS), and ovarian disorder such as fragile X-associated primary ovarian insufficiency (FXPOI). CGG repeats containing FMR1 transcripts form the toxic ribonuclear aggregates, abrupt pre-mRNA splicing, and cause repeat-associated non-AUG translation, leading to the disease symptoms. Here, we utilized a small molecule library of ~ 250,000 members obtained from the National Cancer Institute (NCI) and implemented a shape-based screening approach to identify the candidate small molecules that mitigate toxic CGG RNA-mediated pathogenesis. The compounds obtained from screening were further assessed for their affinity and selectivity towards toxic CGG repeat RNA by employing fluorescence-binding experiment and isothermal calorimetry titration assay. Three candidate molecules B1, B4, and B11 showed high affinity and selectivity for expanded CGG repeats RNA. Further, NMR spectroscopy, gel mobility shift assay, CD spectroscopy, UV-thermal denaturation assay, and molecular docking affirmed their high affinity and selectivity for toxic CGG RNAs. Next, these lead compounds selectively improved the pre-mRNA alternative splicing defects with no perturbation in global splicing efficacy and simultaneously reduced the FMR1polyG protein aggregate formation without affecting the downstream expression of the gene. Taken together these findings, we addressed compound B1, B4, and B11 as potential lead molecules for developing promising therapeutics against FXTAS. Herein, this study, we have utilized shape similarity approach to screen the NCI library and found out the potential candidate which improves the pre-mRNA splicing defects and reduces FMR1polyG aggregations.
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8
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Gao J, Liu N, Zhang X, Yang E, Song Y, Zhang J, Han Q. Utilizing the DNA Aptamer to Determine Lethal α-Amanitin in Mushroom Samples and Urine by Magnetic Bead-ELISA (MELISA). Molecules 2022; 27:molecules27020538. [PMID: 35056853 PMCID: PMC8779134 DOI: 10.3390/molecules27020538] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/12/2022] [Accepted: 01/12/2022] [Indexed: 02/01/2023] Open
Abstract
Amanita poisoning is one of the most deadly types of mushroom poisoning. α-Amanitin is the main lethal toxin in amanita, and the human-lethal dose is about 0.1 mg/kg. Most of the commonly used detection techniques for α-amanitin require expensive instruments. In this study, the α-amanitin aptamer was selected as the research object, and the stem-loop structure of the original aptamer was not damaged by truncating the redundant bases, in order to improve the affinity and specificity of the aptamer. The specificity and affinity of the truncated aptamers were determined using isothermal titration calorimetry (ITC) and gold nanoparticles (AuNPs), and the affinity and specificity of the aptamers decreased after truncation. Therefore, the original aptamer was selected to establish a simple and specific magnetic bead-based enzyme linked immunoassay (MELISA) method for α-amanitin. The detection limit was 0.369 μg/mL, while, in mushroom it was 0.372 μg/mL and in urine 0.337 μg/mL. Recovery studies were performed by spiking urine and mushroom samples with α-amanitin, and these confirmed the desirable accuracy and practical applicability of our method. The α-amanitin and aptamer recognition sites and binding pockets were investigated in an in vitro molecular docking environment, and the main binding bases of both were T3, G4, C5, T6, T7, C67, and A68. This study truncated the α-amanitin aptamer and proposes a method of detecting α-amanitin.
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Affiliation(s)
| | | | | | | | | | | | - Qinqin Han
- Correspondence: ; Tel.: +86-(0871)-65939528
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9
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Ghosh R, Kishore N. Mechanistic physicochemical insights into glycation and drug binding by serum albumin: Implications in diabetic conditions. Biochimie 2021; 193:16-37. [PMID: 34688791 DOI: 10.1016/j.biochi.2021.10.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 09/16/2021] [Accepted: 10/15/2021] [Indexed: 11/02/2022]
Abstract
The drug binding ability of serum albumin might get affected as a result of its glycation under diabetic conditions. It requires not only an understanding of the effect of glycation of the protein upon association with the drug, but also calls for an assessment of structure-property-energetics relationships. A combination of ultrasensitive calorimetric, spectroscopic and chromatographic approach has been employed to correlate thermodynamic signatures with recognition, conformation and mechanistic details of the processes involved. An important observation from this work is that 3-(dansylamino) phenyl boronic acid (DnsPBA) assay cannot always determine the extent of glycation as evidenced by MALDI-TOF mass spectra of glycated HSA due to its selectivity for 1,2 or 1,3 cis-diol structures which may be absent in certain AGEs. Protein gets modified post glycation with the formation of advanced glycation end products (AGEs), which are monitored to be targeted by the guanidine group present in anti-diabetic drugs. AGEs formed in the third and fourth week of glycation are significant in the recognition of anti-diabetic drugs. The results with metformin and aminoguanidine suggest that the extent of binding depends upon the number of guanidine group(s) in the drug molecule. Open chain molecules having guanidine group(s) exhibit stronger affinity towards glycated HSA than closed ring entities like naphthalene or pyridine moiety. The observation that the drug binding ability of HSA is not adversely affected, rather strengthened upon glycation, has implications in diabetic conditions. A rigorous structure-property-energetics correlation based on thermodynamic signatures and identification of functional groups on drugs for recognition by HSA are essential in deriving guidelines for rational drug design addressing diabetes.
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Affiliation(s)
- Ritutama Ghosh
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India
| | - Nand Kishore
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India.
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10
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Judy E, Kishore N. Discrepancies in Thermodynamic Information Obtained from Calorimetry and Spectroscopy in Ligand Binding Reactions: Implications on Correct Analysis in Systems of Biological Importance. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20200248] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Eva Judy
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai – 400 076, India
| | - Nand Kishore
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai – 400 076, India
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11
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Thermodynamic analysis of cooperative ligand binding by the ATP-binding DNA aptamer indicates a population-shift binding mechanism. Sci Rep 2020; 10:18944. [PMID: 33144644 PMCID: PMC7609719 DOI: 10.1038/s41598-020-76002-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 10/22/2020] [Indexed: 01/27/2023] Open
Abstract
The ATP-binding DNA aptamer is often used as a model system for developing new aptamer-based biosensor methods. This aptamer follows a structure-switching binding mechanism and is unusual in that it binds two copies of its ligand. We have used isothermal titration calorimetry methods to study the binding of ATP, ADP, AMP and adenosine to the ATP-binding aptamer. Using both individual and global fitting methods, we show that this aptamer follows a positive cooperative binding mechanism. We have determined the binding affinity and thermodynamics for both ligand-binding sites. By separating the ligand-binding sites by an additional four base pairs, we engineered a variant of this aptamer that binds two adenosine ligands in an independent manner. Together with NMR and thermal stability experiments, these data indicate that the ATP-binding DNA aptamer follows a population-shift binding mechanism that is the source of the positive binding cooperativity by the aptamer.
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12
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Shi C, Deng J, Chiu M, Chen YX, O'Brien ER. Heat shock protein 27 immune complex altered signaling and transport (ICAST): Novel mechanisms of attenuating inflammation. FASEB J 2020; 34:14287-14301. [PMID: 32888229 DOI: 10.1096/fj.202001389rr] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 08/06/2020] [Accepted: 08/07/2020] [Indexed: 01/04/2023]
Abstract
Blood levels of heat shock protein (HSP27) and natural IgG auto-antibodies to HSP27 (AAbs) are higher in healthy controls compared to cardiovascular disease patients. Vaccination of mice with recombinant HSP25 (rHSP25, murine ortholog of human rHSP27) increased AAb levels, attenuated atherogenesis and reduced plaque inflammation and cholesterol content. We sought to determine if the HSP27 immune complex (IC) altered MΦ inflammation signaling (Toll Like Receptor 4; TLR4), and scavenger receptors involved in cholesterol uptake (SR-AI, CD-36). Combining a validated polyclonal IgG anti-HSP27 antibody (PAb) with rHSP27 enhanced binding to THP-1 MΦ cell membranes and activation of NF-κB signaling via TLR4, competing away LPS and effecting an anti-inflammatory cytokine profile. Similarly, adding the PAb with rHSP27 enhanced binding to SR-AI and CD-36, as well as lowered oxLDL binding in HEK293 cells separately transfected with SR-AI and CD-36, or THP-1 MΦ. Finally, the PAb enhanced the uptake and internalization of rHSP27 in THP-1 MΦ. Thus, the HSP27 IC potentiates HSP27 cell membrane signaling with receptors involved in modulating inflammation and cholesterol uptake, as well as HSP27 internalization. Going forward, we are focusing on the development of HSP27 Immune Complex Altered Signaling and Transport (ICAST) as a means of modulating inflammation.
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Affiliation(s)
- Chunhua Shi
- Division of Cardiology, Department of Cardiac Sciences, University of Calgary Cumming School of Medicine, Libin Cardiovascular Institute, Calgary, AB, Canada
| | - Jingti Deng
- Division of Cardiology, Department of Cardiac Sciences, University of Calgary Cumming School of Medicine, Libin Cardiovascular Institute, Calgary, AB, Canada
| | - Michael Chiu
- Division of Cardiology, Department of Cardiac Sciences, University of Calgary Cumming School of Medicine, Libin Cardiovascular Institute, Calgary, AB, Canada
| | - Yong-Xiang Chen
- Division of Cardiology, Department of Cardiac Sciences, University of Calgary Cumming School of Medicine, Libin Cardiovascular Institute, Calgary, AB, Canada
| | - Edward R O'Brien
- Division of Cardiology, Department of Cardiac Sciences, University of Calgary Cumming School of Medicine, Libin Cardiovascular Institute, Calgary, AB, Canada
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13
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Slavkovic S, Eisen SR, Johnson PE. Designed Alteration of Binding Affinity in Structure-Switching Aptamers through the Use of Dangling Nucleotides. Biochemistry 2020; 59:663-670. [PMID: 31912723 DOI: 10.1021/acs.biochem.9b00630] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ability to change binding affinity in a controlled fashion is a key step in the rational design of biomolecules in general and functional nucleic acids in particular. Here, we use dangling nucleotides to alter the binding affinity of structure-switching aptamers. Dangling nucleotides can stabilize or destabilize a nucleic acid structure with a known ΔG°37. When the dangling nucleotide stabilizes the structure, less free energy from ligand binding is needed to fold the molecule and hence the ligand is observed to bind tighter than in the absence of the unpaired nucleotide. For a destabilizing dangling nucleotide, the opposite occurs, and the observed binding is weaker. We demonstrate this concept using both the cocaine-binding aptamer and the ATP-binding aptamer systems. We find that for both aptamers there is a direct, but different, relationship between the predicted stabilization and the change in the observed binding free energy.
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Affiliation(s)
- Sladjana Slavkovic
- Department of Chemistry and Centre for Research on Biomolecular Interactions , York University , Toronto , Ontario , Canada M3J 1P3
| | - Sophie R Eisen
- Department of Chemistry and Centre for Research on Biomolecular Interactions , York University , Toronto , Ontario , Canada M3J 1P3
| | - Philip E Johnson
- Department of Chemistry and Centre for Research on Biomolecular Interactions , York University , Toronto , Ontario , Canada M3J 1P3
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14
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Bernacchi S, Ennifar E. Analysis of the HIV-1 Genomic RNA Dimerization Initiation Site Binding to Aminoglycoside Antibiotics Using Isothermal Titration Calorimetry. Methods Mol Biol 2020; 2113:237-250. [PMID: 32006318 DOI: 10.1007/978-1-0716-0278-2_16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Isothermal titration calorimetry (ITC) provides a sensitive, powerful, and accurate tool to suitably analyze the thermodynamic of RNA binding events. This approach does not require any modification or labeling of the system under analysis and is performed in solution. ITC is a very convenient technique that provides an accurate determination of binding parameters, as well as a complete thermodynamic profile of the molecular interactions. Here we show how this approach can be used to characterize the interactions between the dimerization initiation site (DIS) RNA localized within the HIV-1 viral genome and aminoglycoside antibiotics. Our ITC study showed that the 4,5-disubstituted 2-desoxystreptamine (2-DOS) aminoglycosides can bind the DIS with a nanomolar affinity and a high specificity.
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Affiliation(s)
- Serena Bernacchi
- Architecture et Réactivité de l'ARN - CNRS UPR 9002, Institut de Biologie Moléculaire et Cellulaire, Université de Strasbourg, Strasbourg, France.
| | - Eric Ennifar
- Architecture et Réactivité de l'ARN - CNRS UPR 9002, Institut de Biologie Moléculaire et Cellulaire, Université de Strasbourg, Strasbourg, France.
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15
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Cai S, Yan J, Xiong H, Liu Y, Peng D, Liu Z. Investigations on the interface of nucleic acid aptamers and binding targets. Analyst 2019; 143:5317-5338. [PMID: 30357118 DOI: 10.1039/c8an01467a] [Citation(s) in RCA: 158] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Nucleic acid aptamers are single-stranded DNA or RNA of 20-100 nucleotides in length that have attracted substantial scientific interest due to their ability to specifically bind to target molecules via the formation of three-dimensional structures. Compared to traditional protein antibodies, aptamers have several advantages, such as their small size, high binding affinity, specificity, flexible structure, being chemical synthesizable and modifiable, good biocompatibility, high stability and low immunogenicity, which all contribute to their widely applications in the biomedical field. To date, much progress has been made in the study and applications of aptamers, however, detailed information on how aptamers bind to their targets is still scarce. Over the past few decades, many methods have been introduced to investigate the aptamer-target binding process, such as measuring the main kinetic or thermodynamic parameters, detecting the structural changes of the binding complexes, etc. Apart from traditional physicochemical methods, various types of molecular docking programs have been applied to simulate the aptamer-target interactions, while these simulations also have limitations. To facilitate the further research on the interactions, herein, we provide a brief review to illustrate the recent advances in the study of aptamer-target interactions. We summarize the binding targets of aptamers, such as small molecules, macromolecules, and even cells. Their binding constants (KD) are also summarized. Methods to probe the aptamer-target binding process, such as surface plasmon resonance (SPR), circular dichroism spectroscopy (CD), isothermal titration calorimetry (ITC), footprinting assay, truncation and mutation assay, nuclear magnetic resonance spectroscopy (NMR), X-ray crystallography and molecular docking simulation are indicated. The binding forces mediating the aptamer-target interactions, such as hydrogen bonding, electrostatic interaction, the hydrophobic effect, π-π stacking and van der Waals forces are summarized. The challenges and future perspectives are also discussed.
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Affiliation(s)
- Shundong Cai
- Department of Pharmaceutics, Xiangya School of Pharmaceutical Sciences, Central South University, Changsha, 410013, PR China.
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16
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Nguyen TH, Rustenburg AS, Krimmer SG, Zhang H, Clark JD, Novick PA, Branson K, Pande VS, Chodera JD, Minh DDL. Bayesian analysis of isothermal titration calorimetry for binding thermodynamics. PLoS One 2018; 13:e0203224. [PMID: 30212471 PMCID: PMC6136728 DOI: 10.1371/journal.pone.0203224] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 08/16/2018] [Indexed: 12/04/2022] Open
Abstract
Isothermal titration calorimetry (ITC) is the only technique able to determine both the enthalpy and entropy of noncovalent association in a single experiment. The standard data analysis method based on nonlinear regression, however, provides unrealistically small uncertainty estimates due to its neglect of dominant sources of error. Here, we present a Bayesian framework for sampling from the posterior distribution of all thermodynamic parameters and other quantities of interest from one or more ITC experiments, allowing uncertainties and correlations to be quantitatively assessed. For a series of ITC measurements on metal:chelator and protein:ligand systems, the Bayesian approach yields uncertainties which represent the variability from experiment to experiment more accurately than the standard data analysis. In some datasets, the median enthalpy of binding is shifted by as much as 1.5 kcal/mol. A Python implementation suitable for analysis of data generated by MicroCal instruments (and adaptable to other calorimeters) is freely available online.
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Affiliation(s)
- Trung Hai Nguyen
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL, United States of America
| | - Ariën S. Rustenburg
- Computational and Systems Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, United States of America
- Graduate Program in Physiology, Biophysics, and Systems Biology, Weill Cornell Medical College, New York, NY, United States of America
| | - Stefan G. Krimmer
- Department of Pharmaceutical Chemistry, University of Marburg, Marbacher Weg 6, Marburg, Germany
| | - Hexi Zhang
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL, United States of America
| | - John D. Clark
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL, United States of America
| | - Paul A. Novick
- Department of Chemistry, Stanford University, Stanford, CA, United States of America
| | - Kim Branson
- Department of Chemistry, Stanford University, Stanford, CA, United States of America
| | - Vijay S. Pande
- Department of Chemistry, Stanford University, Stanford, CA, United States of America
| | - John D. Chodera
- Computational and Systems Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, United States of America
- * E-mail: (JDC); (DDLM)
| | - David D. L. Minh
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL, United States of America
- * E-mail: (JDC); (DDLM)
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17
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Differential interaction behaviors of an alkaloid drug with DMPG liposome membrane as a function of the phase state of the lipid: Nonionic surfactant-induced solubilization of the lipid. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2017.12.152] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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18
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Beyeh NK, Díez I, Taimoory SM, Meister D, Feig AI, Trant JF, Ras RHA, Rissanen K. High-affinity and selective detection of pyrophosphate in water by a resorcinarene salt receptor. Chem Sci 2017; 9:1358-1367. [PMID: 29675184 PMCID: PMC5887233 DOI: 10.1039/c7sc05167k] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 12/15/2017] [Indexed: 11/21/2022] Open
Abstract
Pyrophosphate (PPi) is a byproduct of DNA and RNA synthesis, and abnormal levels are indicative of disease. We report the high-affinity binding of PPi in water by N-alkyl ammonium resorcinarene chloride receptors. Experimental analysis using 1H and 31P NMR, isothermal titration calorimetry, mass spectrometry, and UV-vis spectroscopy all support exceptional selectivity of these systems for PPi in water. The measured affinity of K1 = 1.60 × 107 M-1 for PPi is three orders of magnitude larger than that observed for binding to another phosphate, ATP. This exceptional anion-binding affinity in water is explored through a detailed density functional theory computational study. These systems provide a promising avenue for the development of future innovative medical diagnostic tools.
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Affiliation(s)
- Ngong Kodiah Beyeh
- Aalto University , School of Science , Department of Applied Physics , Puumiehenkuja 2 , FI-02150 , Espoo , Finland . ; .,University of Windsor , Department of Chemistry and Biochemistry , Windsor , ON N9B 3P4 , Canada .
| | - Isabel Díez
- Aalto University , School of Science , Department of Applied Physics , Puumiehenkuja 2 , FI-02150 , Espoo , Finland . ;
| | - S Maryamdokht Taimoory
- University of Windsor , Department of Chemistry and Biochemistry , Windsor , ON N9B 3P4 , Canada .
| | - Daniel Meister
- University of Windsor , Department of Chemistry and Biochemistry , Windsor , ON N9B 3P4 , Canada .
| | - Andrew I Feig
- Wayne State University , Department of Chemistry , 5101 Cass Ave. , Detroit , MI 48202 , USA
| | - John F Trant
- University of Windsor , Department of Chemistry and Biochemistry , Windsor , ON N9B 3P4 , Canada .
| | - Robin H A Ras
- Aalto University , School of Science , Department of Applied Physics , Puumiehenkuja 2 , FI-02150 , Espoo , Finland . ; .,Aalto University , School of Chemical Engineering , Department of Bioproducts and Biosystems , Kemistintie 1 , 02150 Espoo , Finland
| | - Kari Rissanen
- University of Jyvaskyla , Department of Chemistry , P. O. Box 35 , FI-40014 Jyväskylä , Finland .
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19
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Basu P, Suresh Kumar G. Small molecule-RNA recognition: Binding of the benzophenanthridine alkaloids sanguinarine and chelerythrine to single stranded polyribonucleotides. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2017; 174:173-181. [PMID: 28779690 DOI: 10.1016/j.jphotobiol.2017.07.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 07/18/2017] [Accepted: 07/21/2017] [Indexed: 01/18/2023]
Abstract
Single stranded RNAs are biologically potent as they participate in various key cellular processes. The binding efficacy of two potent anticancer alkaloids, sanguinarine (here after SANG) and chelerythrine (here after CHEL), with single-stranded ribonucleic acids poly(rI), poly(rG), and poly(rC) were studied using spectroscopic and thermodynamic tools. Results reveal that both SANG and CHEL binds well with single stranded RNAs with affinity in the order poly(rI)>poly(rG)>poly(rC). CHEL showed slightly higher affinity compared to SANG with all the single stranded RNAs. Both SANG and CHEL showed association affinity of the lower 106 order with poly(rI), higher 105 order binding with poly(rG) and lower 105 order with poly(rC). The binding mode was partial intercalation due to the staking interaction between the bases and the alkaloids. The complexation of both the SANG and CHEL to the RNAs were mainly enthalpy driven and also favoured by entropy changes. Perturbation was observed in the RNA conformation due to binding of the alkaloids. In this present study we have deciphered the fundamental structural and calorimetric aspects of the interaction of the natural benzophenanthridine alkaloids with single stranded RNAs and these results may help to develop new generation alkaloid based therapeutics targeting single stranded RNAs.
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Affiliation(s)
- Pritha Basu
- Organic and Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700 032, India
| | - Gopinatha Suresh Kumar
- Organic and Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700 032, India.
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20
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Identification of N 6-methyladenosine reader proteins. Methods 2017; 126:105-111. [PMID: 28454774 DOI: 10.1016/j.ymeth.2017.04.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 04/20/2017] [Accepted: 04/21/2017] [Indexed: 11/21/2022] Open
Abstract
The reversible N6-methyladenosine (m6A) modification of eukaryotic messenger RNAs (mRNAs) is a widespread regulatory mechanism that impacts every step in the mRNA life cycle. The effect of m6A on mRNA fate depends on the binding of "m6A reader" proteins - RNA binding proteins that specifically bind to RNAs containing m6A. Here, we describe an RNA pull-down method that can be used to identify novel m6A reader proteins starting from a known m6A-modified site in cellular or viral RNA. We further describe how a combination of immunoprecipitation-based sequencing methods can be used to identify m6A-modified sites bound by an m6A reader protein on a transcriptome-wide level. The discovery of new m6A reader proteins and their m6A-modified targets would provide further insight into the mechanisms and functions of m6A in the cell.
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21
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Echterbille J, Gilles N, Araóz R, Mourier G, Amar M, Servent D, De Pauw E, Quinton L. Discovery and characterization of EII B, a new α-conotoxin from Conus ermineus venom by nAChRs affinity capture monitored by MALDI-TOF/TOF mass spectrometry. Toxicon 2017; 130:1-10. [PMID: 28238803 DOI: 10.1016/j.toxicon.2017.02.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 02/03/2017] [Accepted: 02/20/2017] [Indexed: 12/13/2022]
Abstract
Animal toxins are peptides that often bind with remarkable affinity and selectivity to membrane receptors such as nicotinic acetylcholine receptors (nAChRs). The latter are, for example, targeted by α-conotoxins, a family of peptide toxins produced by venomous cone snails. nAChRs are implicated in numerous physiological processes explaining why the design of new pharmacological tools and the discovery of potential innovative drugs targeting these receptor channels appear so important. This work describes a methodology developed to discover new ligands of nAChRs from complex mixtures of peptides. The methodology was set up by the incubation of Torpedo marmorata electrocyte membranes rich in nAChRs with BSA tryptic digests (>100 peptides) doped by small amounts of known nAChRs ligands (α-conotoxins). Peptides that bind to the receptors were purified and analyzed by MALDI-TOF/TOF mass spectrometry which revealed an enrichment of α-conotoxins in membrane-containing fractions. This result exhibits the binding of α-conotoxins to nAChRs. Negative controls were performed to demonstrate the specificity of the binding. The usefulness and the power of the methodology were also investigated for a discovery issue. The workflow was then applied to the screening of Conus ermineus crude venom, aiming at characterizing new nAChRs ligands from this venom, which has not been extensively investigated to date. The methodology validated our experiments by allowing us to bind two α-conotoxins (α-EI and α-EIIA) which have already been described as nAChRs ligands. Moreover, a new conotoxin, never described to date, was also captured, identified and sequenced from this venom. Classical pharmacology tests by radioligand binding using a synthetic homologue of the toxin confirm the activity of the new peptide, called α-EIIB. The Ki value of this peptide for Torpedo nicotinic receptors was measured at 2.2 ± 0.7 nM.
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Affiliation(s)
- Julien Echterbille
- Laboratory of Mass Spectrometry- MolSys, Department of Chemistry, University of Liege, Liege, Belgium
| | - Nicolas Gilles
- Service d'Ingénierie Moléculaire des Protéines (SIMOPRO), IBITECS, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette, France
| | - Romulo Araóz
- Service d'Ingénierie Moléculaire des Protéines (SIMOPRO), IBITECS, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette, France
| | - Gilles Mourier
- Service d'Ingénierie Moléculaire des Protéines (SIMOPRO), IBITECS, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette, France
| | - Muriel Amar
- Service d'Ingénierie Moléculaire des Protéines (SIMOPRO), IBITECS, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette, France
| | - Denis Servent
- Service d'Ingénierie Moléculaire des Protéines (SIMOPRO), IBITECS, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette, France
| | - Edwin De Pauw
- Laboratory of Mass Spectrometry- MolSys, Department of Chemistry, University of Liege, Liege, Belgium
| | - Loic Quinton
- Laboratory of Mass Spectrometry- MolSys, Department of Chemistry, University of Liege, Liege, Belgium.
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22
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Börner R, Kowerko D, Miserachs HG, Schaffer MF, Sigel RK. Metal ion induced heterogeneity in RNA folding studied by smFRET. Coord Chem Rev 2016. [DOI: 10.1016/j.ccr.2016.06.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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23
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Butko MT, Moree B, Mortensen RB, Salafsky J. Detection of Ligand-Induced Conformational Changes in Oligonucleotides by Second-Harmonic Generation at a Supported Lipid Bilayer Interface. Anal Chem 2016; 88:10482-10489. [PMID: 27696827 DOI: 10.1021/acs.analchem.6b02498] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
There is a high demand for characterizing oligonucleotide structural changes associated with binding interactions as well as identifying novel binders that modulate their structure and function. In this study, second-harmonic generation (SHG) was used to study RNA and DNA oligonucleotide conformational changes associated with ligand binding. For this purpose, we developed an avidin-based biotin capture surface based on a supported lipid bilayer membrane. The technique was applied to two well-characterized aptamers, both of which undergo conformational changes upon binding either a protein or a small molecule ligand. In both cases, SHG was able to resolve conformational changes in these oligonucleotides sensitively and specifically, in solution and in real time, using nanogram amounts of material. In addition, we developed a competition assay for the oligonucleotides between the specific ligands and known, nonspecific binders, and we demonstrated that intercalators and minor groove binders affect the conformation of the DNA and RNA oligonucleotides in different ways upon binding and subsequently block specific ligand binding in all cases. Our work demonstrates the broad potential of SHG for studying oligonucleotides and their conformational changes upon interaction with ligands. As SHG offers a powerful, high-throughput screening approach, our results here also open an important new avenue for identifying novel chemical probes or sequence-targeted drugs that disrupt or modulate DNA or RNA structure and function.
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Affiliation(s)
- Margaret T Butko
- Biodesy, Inc. , 384 Oyster Point Boulevard, Suite No. 8, South San Francisco, California 94080, United States
| | - Ben Moree
- Biodesy, Inc. , 384 Oyster Point Boulevard, Suite No. 8, South San Francisco, California 94080, United States
| | - Richard B Mortensen
- Biodesy, Inc. , 384 Oyster Point Boulevard, Suite No. 8, South San Francisco, California 94080, United States
| | - Joshua Salafsky
- Biodesy, Inc. , 384 Oyster Point Boulevard, Suite No. 8, South San Francisco, California 94080, United States
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24
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Isothermal Titration Calorimetry: Assisted Crystallization of RNA-Ligand Complexes. Methods Mol Biol 2016; 1320:127-43. [PMID: 26227041 DOI: 10.1007/978-1-4939-2763-0_9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
The success rate of nucleic acids/ligands co-crystallization can be significantly improved by performing preliminary biophysical analyses. Among suitable biophysical approaches, isothermal titration calorimetry (ITC) is certainly a method of choice. ITC can be used in a wide range of experimental conditions to monitor in real time the formation of the RNA- or DNA-ligand complex, with the advantage of providing in addition the complete binding profile of the interaction. Following the ITC experiment, the complex is ready to be concentrated for crystallization trials. This chapter describes a detailed experimental protocol for using ITC as a tool for monitoring RNA/small molecule binding, followed by co-crystallization.
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25
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Guhathakurta B, Basu P, Kumar GS, Lu L, Zhu M, Bandyopadhyay N, Naskar JP. Synthetic, structural, electrochemical and DNA-binding aspects of a novel oximato bridged copper(II) dimer. Polyhedron 2016. [DOI: 10.1016/j.poly.2016.03.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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26
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Wang B, Jia Y, Lin Q. A microfabrication-based approach to quantitative isothermal titration calorimetry. Biosens Bioelectron 2016; 78:438-446. [DOI: 10.1016/j.bios.2015.11.069] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 11/19/2015] [Accepted: 11/24/2015] [Indexed: 10/22/2022]
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27
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Characterization of the full-length btuB riboswitch from Klebsiella pneumoniae. J Inorg Biochem 2015; 160:106-13. [PMID: 26765998 DOI: 10.1016/j.jinorgbio.2015.12.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 12/05/2015] [Accepted: 12/16/2015] [Indexed: 12/14/2022]
Abstract
Riboswitches are cis-regulatory RNA elements on the mRNA level that control the expression of the downstream coding region. The interaction of the riboswitch with its specific metabolite, which is related to the function of the controlled gene, induces a structural change of the RNA architecture. Consequently, gene regulation is induced by un/masking of the ribosome binding site (RBS). In the genome of Klebsiella pneumoniae a sequence was identified by bioinformatics and proposed to be a B12 riboswitch regulated by coenzyme B12. Here we study this new coenzyme B12-dependent riboswitch system by in-line probing and ITC. The riboswitch sequence includes the whole expression platform as well as RBS. In-line probing experiments were performed to investigate the structural rearrangement of this 243-nt long RNA sequence while Isothermal Titration Calorimetry (ITC) yielded the thermodynamic parameters of the interaction between the riboswitch and its metabolite. The interaction of coenzyme B12 with the butB riboswitch of K. pneumoniae is an exothermic process with a 1:1 binding stoichiometry and binding affinities of log KA=6.73±0.02 at 15°C and log KA=6.00±0.09 at 30°C.
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28
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Alguacil J, Robles J, Ràfols C, Bosch E. Binding thermodynamics of paromomycin, neomycin, neomycin-dinucleotide and -diPNA conjugates to bacterial and human rRNA. J Mol Recognit 2015; 29:142-50. [DOI: 10.1002/jmr.2513] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Revised: 09/18/2015] [Accepted: 09/19/2015] [Indexed: 01/19/2023]
Affiliation(s)
- Javier Alguacil
- Departament de Química Orgànica; Facultat de Química and Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona; Martí i Franquès, 1-11 08028 Barcelona Spain
| | - Jordi Robles
- Departament de Química Orgànica; Facultat de Química and Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona; Martí i Franquès, 1-11 08028 Barcelona Spain
| | - Clara Ràfols
- Departament de Química Analítica; Facultat de Química and Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona; Martí i Franquès, 1-11 08028 Barcelona Spain
| | - Elisabeth Bosch
- Departament de Química Analítica; Facultat de Química and Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona; Martí i Franquès, 1-11 08028 Barcelona Spain
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29
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Liu J, Zeng C, Hogan V, Zhou S, Monwar MM, Hines JV. Identification of Spermidine Binding Site in T-box Riboswitch Antiterminator RNA. Chem Biol Drug Des 2015; 87:182-9. [PMID: 26348362 DOI: 10.1111/cbdd.12660] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 07/24/2015] [Accepted: 08/14/2015] [Indexed: 01/08/2023]
Abstract
The T-box transcription antitermination riboswitch controls bacterial gene expression by structurally responding to uncharged, cognate tRNA. Previous studies indicated that cofactors, such as the polyamine spermidine, might serve a specific functional role in enhancing riboswitch efficacy. As riboswitch function depends on key RNA structural changes involving the antiterminator element, the interaction of spermidine with the T-box riboswitch antiterminator element was investigated. Spermidine binds antiterminator model RNA with high affinity (micromolar Kd ) based on isothermal titration calorimetry and fluorescence-monitored binding assays. NMR titration studies, molecular modeling, and inline and enzymatic probing studies indicate that spermidine binds at the 3' portion of the highly conserved seven-nucleotide bulge in the antiterminator. Together, these results support the conclusion that spermidine binds the T-box antiterminator RNA preferentially in a location important for antiterminator function. The implications of these findings are significant both for better understanding of the T-box riboswitch mechanism and for antiterminator-targeted drug discovery efforts.
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Affiliation(s)
- Jia Liu
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
| | - Chunxi Zeng
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
| | - Vivian Hogan
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
| | - Shu Zhou
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
| | - Md Masud Monwar
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
| | - Jennifer V Hines
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
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30
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Wohlgemuth I, Lenz C, Urlaub H. Studying macromolecular complex stoichiometries by peptide-based mass spectrometry. Proteomics 2015; 15:862-79. [PMID: 25546807 PMCID: PMC5024058 DOI: 10.1002/pmic.201400466] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 11/24/2014] [Accepted: 12/22/2014] [Indexed: 11/11/2022]
Abstract
A majority of cellular functions are carried out by macromolecular complexes. A host of biochemical and spectroscopic methods exists to characterize especially protein/protein complexes, however there has been a lack of a universal method to determine protein stoichiometries. Peptide‐based MS, especially as a complementary method to the MS analysis of intact protein complexes, has now been developed to a point where it can be employed to assay protein stoichiometries in a routine manner. While the experimental demands are still significant, peptide‐based MS has been successfully applied to analyze stoichiometries for a variety of protein complexes from very different biological backgrounds. In this review, we discuss the requirements especially for targeted MS acquisition strategies to be used in this context, with a special focus on the interconnected experimental aspects of sample preparation, protein digestion, and peptide stability. In addition, different strategies for the introduction of quantitative peptide standards and their suitability for different scenarios are compared.
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Affiliation(s)
- Ingo Wohlgemuth
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Goettingen, Germany
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31
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Bowater RP, Cobb AM, Pivonkova H, Havran L, Fojta M. Biophysical and electrochemical studies of protein–nucleic acid interactions. MONATSHEFTE FUR CHEMIE 2015. [DOI: 10.1007/s00706-014-1405-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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32
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Basu P, Kumar GS. Structural and thermodynamic basis of interaction of the putative anticancer agent chelerythrine with single, double and triple-stranded RNAs. RSC Adv 2015. [DOI: 10.1039/c5ra00660k] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Interaction of chl with poly(uau), poly(au) and poly(u).
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Affiliation(s)
- Pritha Basu
- Biophysical Chemistry Laboratory
- Chemistry Division
- CSIR-Indian Institute of Chemical Biology
- Kolkata 700 032
- India
| | - Gopinatha Suresh Kumar
- Biophysical Chemistry Laboratory
- Chemistry Division
- CSIR-Indian Institute of Chemical Biology
- Kolkata 700 032
- India
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33
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Khan AY, Saha B, Kumar GS. Interaction of phenazinium dyes with double-stranded poly(A): spectroscopy and isothermal titration calorimetry studies. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2014; 131:615-624. [PMID: 24861262 DOI: 10.1016/j.saa.2014.04.087] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 03/19/2014] [Accepted: 04/14/2014] [Indexed: 06/03/2023]
Abstract
A comprehensive study on the binding of phenazinium dyes viz. janus green B, indoine blue, safranine O and phenosafranine with double stranded poly(A) using various spectroscopic and calorimetric techniques is presented. A higher binding of janus green B and indoine blue over safranine O and phenosafranine to poly(A) was observed from all experiments. Intercalative mode of binding of the dyes was inferred from fluorescence polarization anisotropy, iodide quenching and viscosity experiments. Circular dichroism study revealed significant perturbation of the secondary structure of poly(A) on binding of these dyes. Results from isothermal titration calorimetry experiments suggested that the binding was predominantly entropy driven with a minor contribution of enthalpy to the standard molar Gibbs energy. The results presented here may open new opportunities in the application of these dyes as RNA targeted therapeutic agents.
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Affiliation(s)
- Asma Yasmeen Khan
- Biophysical Chemistry Laboratory, Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700 032, India
| | - Baishakhi Saha
- Biophysical Chemistry Laboratory, Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700 032, India
| | - Gopinatha Suresh Kumar
- Biophysical Chemistry Laboratory, Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700 032, India.
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Halvorsen K, Agris PF. Cross-platform comparison of nucleic acid hybridization: toward quantitative reference standards. Anal Biochem 2014; 465:127-33. [PMID: 25124363 DOI: 10.1016/j.ab.2014.08.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 07/14/2014] [Accepted: 08/02/2014] [Indexed: 11/18/2022]
Abstract
Measuring interactions between biological molecules is vitally important to both basic and applied research as well as development of pharmaceuticals. Although a wide and growing range of techniques is available to measure various kinetic and thermodynamic properties of interacting biomolecules, it can be difficult to compare data across techniques of different laboratories and personnel or even across different instruments using the same technique. Here we evaluate relevant biological interactions based on complementary DNA and RNA oligonucleotides that could be used as reference standards for many experimental systems. We measured thermodynamics of duplex formation using isothermal titration calorimetry, differential scanning calorimetry, and ultraviolet-visible (UV-vis) monitored denaturation/renaturation. These standards can be used to validate results, compare data from disparate techniques, act as a teaching tool for laboratory classes, or potentially to calibrate instruments. The RNA and DNA standards have many attractive features, including low cost, high purity, easily measurable concentrations, and minimal handling concerns, making them ideal for use as a reference material.
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Affiliation(s)
- Ken Halvorsen
- The RNA Institute, University at Albany-SUNY, Albany, NY 12222, USA.
| | - Paul F Agris
- The RNA Institute, University at Albany-SUNY, Albany, NY 12222, USA; Department of Biological Sciences, University at Albany-SUNY, Albany, NY 12222, USA
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35
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Paudel B, Rueda D. RNA folding dynamics using laser-assisted single-molecule refolding. Methods Mol Biol 2014; 1086:289-307. [PMID: 24136611 DOI: 10.1007/978-1-62703-667-2_17] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
RNA folding pathways can be complex and even include kinetic traps or misfolded intermediates that can be slow to resolve. Characterizing these pathways is critical to understanding how RNA molecules acquire their biological function. We have previously developed a novel approach to help characterize such misfolded intermediates. Laser-assisted single-molecule refolding (LASR) is a powerful technique that combines temperature-jump (T-jump) kinetics with single-molecule detection. In a typical LASR experiment, the temperature is rapidly increased and conformational dynamics are characterized, in real-time, at the single-molecule level using single-molecule fluorescence resonance energy transfer (smFRET). Here, we provide detailed protocols for performing LASR experiments including sample preparation, temperature calibration, and data analysis.
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Affiliation(s)
- Bishnu Paudel
- Department of Medicine, Section of Virology, Imperial College, London, UK
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36
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Global analysis of riboswitches by small-angle X-ray scattering and calorimetry. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1839:1020-1029. [PMID: 24769285 DOI: 10.1016/j.bbagrm.2014.04.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 04/10/2014] [Accepted: 04/13/2014] [Indexed: 11/22/2022]
Abstract
Riboswitches are phylogenetically widespread non-coding mRNA domains that directly bind cellular metabolites and regulate transcription, translation, RNA stability or splicing via alternative RNA structures modulated by ligand binding. The details of ligand recognition by many riboswitches have been elucidated using X-ray crystallography and NMR. However, the global dynamics of riboswitch-ligand interactions and their thermodynamic driving forces are less understood. By compiling the work of many laboratories investigating riboswitches using small-angle X-ray scattering (SAXS) and isothermal titration calorimetry (ITC), we uncover general trends and common themes. There is a pressing need for community-wide consensus experimental conditions to allow results of riboswitch studies to be compared rigorously. Nonetheless, our meta-analysis reveals considerable diversity in the extent to which ligand binding reorganizes global riboswitch structures. It also demonstrates a wide spectrum of enthalpy-entropy compensation regimes across riboswitches that bind a diverse set of ligands, giving rise to a relatively narrow range of physiologically relevant free energies and ligand affinities. From the strongly entropy-driven binding of glycine to the predominantly enthalpy-driven binding of c-di-GMP to their respective riboswitches, these distinct thermodynamic signatures reflect the versatile strategies employed by RNA to adapt to the chemical natures of diverse ligands. Riboswitches have evolved to use a combination of long-range tertiary interactions, conformational selection, and induced fit to work with distinct ligand structure, charge, and solvation properties. This article is part of a Special Issue entitled: Riboswitches.
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37
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Khan AY, Saha B, Suresh Kumar G. Phenazinium dyes safranine O and phenosafranine induce self-structure in single stranded polyadenylic acid: structural and thermodynamic studies. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2014; 132:17-26. [PMID: 24565690 DOI: 10.1016/j.jphotobiol.2014.01.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 12/30/2013] [Accepted: 01/19/2014] [Indexed: 11/29/2022]
Abstract
The interaction of phenazinium dyes, safranine O and phenosafranine with single stranded polyadenylic acid was studied using spectroscopic viscometric and calorimetric techniques. Both dyes bind to polyadenylic acid strongly with association constant of the order of 10(5)M(-1). Safranine O showed higher affinity over phenosafranine. The binding induced conformational changes in polyadenylic acid, but the extent of change was much higher with safranine O. The bound safranine O molecules acquired strong induced circular dichroism spectra compared to the weak induced circular dichroism of phenosafranine. Fluorescence polarization, iodide quenching, viscosity results and energy transfer from bases to bound dyes suggested intercalation of the dye molecules to polyadenylic acid structure. The binding was entropy driven in both the cases. Circular dichroism and optical melting studies revealed cooperative melting profiles for dye-polyadenylic acid complexes that provided evidence for the formation of self-structured polyadenylic acid on dye binding. This structural reorganization was further confirmed by differential scanning calorimetry results.
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Affiliation(s)
- Asma Yasmeen Khan
- Biophysical Chemistry Laboratory, Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700 032, India
| | - Baishakhi Saha
- Biophysical Chemistry Laboratory, Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700 032, India
| | - Gopinatha Suresh Kumar
- Biophysical Chemistry Laboratory, Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700 032, India.
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38
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Das A, Kumar GS. Binding studies of aristololactam-β-d-glucoside and daunomycin to human serum albumin. RSC Adv 2014. [DOI: 10.1039/c4ra04327h] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The binding of two carbohydrate containing molecules aristololactam-β-d-glucoside and daunomycin with human serum albumin was evaluated by biophysical techniques.
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Affiliation(s)
- Abhi Das
- Biophysical Chemistry Laboratory
- Chemistry Division
- CSIR-Indian Institute of Chemical Biology
- Kolkata 700 032, India
| | - Gopinatha Suresh Kumar
- Biophysical Chemistry Laboratory
- Chemistry Division
- CSIR-Indian Institute of Chemical Biology
- Kolkata 700 032, India
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39
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Zengeya T, Gindin A, Rozners E. Improvement of sequence selectivity in triple helical recognition of RNA by phenylalanine-derived PNA. ARTIFICIAL DNA, PNA & XNA 2013; 4:69-76. [PMID: 24104925 DOI: 10.4161/adna.26599] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Modified peptide nucleic acids (PNA) containing one or two thymine PNA monomers derived from phenylalanine were synthesized. Triple helix formation by these modified PNAs with RNA and DNA hairpins having a variable base pair in the middle of the helix were studied using isothermal titration calorimetry and compared with triple helix formation by non-modified PNAs. While unmodified PNA had low sequence selectivity against mismatched hairpins, introduction of one or two phenylalanine-derived monomers significantly increased the mismatch discrimination and sequence selectivity of the modified PNA. Consistent with our previous observations, PNA formed more stable triple helices with RNA than with DNA. Interestingly, the phenylalanine modification further improved the preference of PNA for RNA over DNA hairpin.
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Affiliation(s)
- Thomas Zengeya
- Department of Chemistry; Binghamton University; State University of New York; Binghamton, NY USA
| | - Artem Gindin
- Department of Chemistry; Binghamton University; State University of New York; Binghamton, NY USA
| | - Eriks Rozners
- Department of Chemistry; Binghamton University; State University of New York; Binghamton, NY USA
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40
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Molgó J, Aráoz R, Benoit E, Iorga BI. Physical and virtual screening methods for marine toxins and drug discovery targeting nicotinic acetylcholine receptors. Expert Opin Drug Discov 2013; 8:1203-23. [DOI: 10.1517/17460441.2013.822365] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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41
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Huang Y, Lapitsky Y. Determining the colloidal behavior of ionically cross-linked polyelectrolytes with isothermal titration calorimetry. J Phys Chem B 2013; 117:9548-57. [PMID: 23856000 DOI: 10.1021/jp405384b] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Mixtures of polyelectrolytes and multivalent counterions can self-assemble into colloidal complexes. These complexes attract widespread interest in applications such as medicine, household product formulations, and separation processes. To facilitate the development of these colloidal dispersions, we examined isothermal titration calorimetry (ITC) as an automated screening tool for identifying the polymer and multivalent counterion compositions that (1) form ionically cross-linked colloidal complexes and (2) lead to their rapid coagulation (and macroscopic phase separation). By studying various polyelectrolyte/multivalent counterion mixtures, we have identified and generalized the features in the ITC data that indicate colloidal complex formation and coagulation. The limitations of this calorimetric screening method were also elucidated. These analyses suggest that ITC can be effective for screening the short-term colloidal behavior of polyelectrolyte/multivalent counterion mixtures but are unreliable in revealing their long-term (equilibrium) properties.
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Affiliation(s)
- Yan Huang
- Department of Chemical and Environmental Engineering, University of Toledo, Toledo, Ohio 43606, USA
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42
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Bec G, Meyer B, Gerard MA, Steger J, Fauster K, Wolff P, Burnouf D, Micura R, Dumas P, Ennifar E. Thermodynamics of HIV-1 reverse transcriptase in action elucidates the mechanism of action of non-nucleoside inhibitors. J Am Chem Soc 2013; 135:9743-52. [PMID: 23742167 DOI: 10.1021/ja4018418] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
HIV-1 reverse transcriptase (RT) is a heterodimeric enzyme that converts the genomic viral RNA into proviral DNA. Despite intensive biochemical and structural studies, direct thermodynamic data regarding RT interactions with its substrates are still lacking. Here we addressed the mechanism of action of RT and of non-nucleoside RT inhibitors (NNRTIs) by isothermal titration calorimetry (ITC). Using a new incremental-ITC approach, a step-by-step thermodynamic dissection of the RT polymerization activity showed that most of the driving force for DNA synthesis is provided by initial dNTP binding. Surprisingly, thermodynamic and kinetic data led to a reinterpretation of the mechanism of inhibition of NNRTIs. Binding of NNRTIs to preformed RT/DNA complexes is hindered by a kinetic barrier and NNRTIs mostly interact with free RT. Once formed, RT/NNRTI complexes bind DNA either in a seemingly polymerase-competent orientation or form high-affinity dead-end complexes, both RT/NNRTI/DNA complexes being unable to bind the incoming nucleotide substrate.
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Affiliation(s)
- Guillaume Bec
- Architecture et Réactivité des ARN, CNRS/Université de Strasbourg, Institut de Biologie Moléculaire et Cellulaire, 15 rue René Descartes, 67084 Strasbourg, France
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43
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Bhowmik D, Kumar GS. Interaction of 9-O-(ω-amino) alkyl ether berberine analogs with poly(dT)·poly(dA)*poly(dT) triplex and poly(dA)·poly(dT) duplex: a comparative study. Mol Biol Rep 2013; 40:5439-50. [PMID: 23666107 DOI: 10.1007/s11033-013-2642-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 05/03/2013] [Indexed: 10/26/2022]
Abstract
Isoquinoline alkaloids and their analogs represent an important class of molecules for their broad range of clinical and pharmacological utility. These compounds are of current interest owing to their low toxicity and excellent chemo preventive properties. These alkaloids can play important role in stabilising the nucleic acid triple helices. The present study has focused on the interaction of five 9-O-(ω-amino) alkyl ether berberine analogs with the DNA triplex poly(dT)·poly(dA)*poly(dT) and the parent duplex poly(dA)·poly(dT) studied using various biophysical techniques. Scatchard analysis of the spectral data indicated that the analogs bind both to the duplex and triplex in a non-cooperative manner in contrast to the cooperative binding of berberine to the DNA triplex. Strong intercalative binding to the DNA triplex structure was revealed from ferrocyanide quenching, fluorescence polarization and viscosity results. Thermal melting studies demonstrated higher stabilization of the Hoogsteen base paired third strand of the DNA triplex compared to the Watson-Crick strand. Circular dichroism studies suggested a stronger perturbation of the DNA triplex conformation by the alkaloid analogs compared to the duplex. The binding was entropy-driven in each case and the entropy contribution to free energy increased as the length of the alkyl side chain increased. The analogs exhibited stronger binding affinity to the triple helical structure compared to the parent double helical structure.
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Affiliation(s)
- Debipreeta Bhowmik
- Biophysical Chemistry Laboratory, Chemistry Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C. Mullick Road, Kolkata, 700 032, India
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Kundu S, Biswas MK, Banerjee A, Bhadra K, Kumar GS, Drew MGB, Bhadra R, Ghosh P. Synthesis, structure and DNA binding studies of 9-phenyldibenzo[a,c] phenazin-9-ium. RSC Adv 2013. [DOI: 10.1039/c2ra22317a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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45
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Khan AY, Hossain M, Kumar GS. Binding of plant alkaloids berberine and palmatine to serum albumins: a thermodynamic investigation. Mol Biol Rep 2012; 40:553-66. [DOI: 10.1007/s11033-012-2092-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 10/03/2012] [Indexed: 01/29/2023]
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46
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Blakeley BD, DePorter SM, Mohan U, Burai R, Tolbert BS, McNaughton BR. Methods for identifying and characterizing interactions involving RNA. Tetrahedron 2012. [DOI: 10.1016/j.tet.2012.07.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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47
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Das A, Suresh Kumar G. Probing the binding of two sugar bearing anticancer agents aristololactam-β-(D)-glucoside and daunomycin to double stranded RNA polynucleotides: a combined spectroscopic and calorimetric study. MOLECULAR BIOSYSTEMS 2012; 8:1958-69. [PMID: 22596256 DOI: 10.1039/c2mb25080b] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The plant alkaloid aristololactam-β-d-glucoside and the anticancer chemotherapy drug daunomycin are two sugar bearing DNA binding antibiotics. The binding of these molecules to three double stranded ribonucleic acids, poly(A)·poly(U), poly(I)·poly(C) and poly(C)·poly(G), was studied using various biophysical techniques. Absorbance and fluorescence studies revealed that these molecules bound non-cooperatively to these ds RNAs with the binding affinities of the order 10(6) for daunomycin and 10(5) M(-1) for aristololactam-β-d-glucoside. Fluorescence quenching and viscosity studies gave evidence for intercalative binding. The binding enhanced the melting temperature of poly(A)·poly(U) and poly(I)·poly(C) and the binding affinity values evaluated from the melting data were in agreement with that obtained from other techniques. Circular dichroism results suggested minor conformational perturbations of the RNA structures. The binding was characterized by negative enthalpy and positive entropy changes and the affinity constants derived from calorimetry were in agreement with that obtained from spectroscopic data. Daunomycin bound all the three RNAs stronger than aristololactam-β-d-glucoside and the binding affinity varied as poly(A)·poly(U) > poly(I)·poly(C) > poly(C)·poly(G). The temperature dependence of the enthalpy changes yielded negative values of heat capacity changes for the complexation suggesting substantial hydrophobic contribution to the binding process. Furthermore, an enthalpy-entropy compensation behavior was also seen in all systems. These results provide new insights into binding of these small molecule drugs to double stranded RNA sequences.
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Affiliation(s)
- Abhi Das
- Biophysical Chemistry Laboratory, Chemistry Division, CSIR - Indian Institute of Chemical Biology, 4, Raja S. C. Mullick Road, Kolkata 700 032, India
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48
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Thermodynamic and kinetic analysis of an RNA kissing interaction and its resolution into an extended duplex. Biophys J 2012; 102:1097-107. [PMID: 22404932 DOI: 10.1016/j.bpj.2011.12.052] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Revised: 12/22/2011] [Accepted: 12/30/2011] [Indexed: 11/22/2022] Open
Abstract
Kissing hairpin interactions form when the loop residues of two hairpins have Watson-Crick complementarity. In a unimolecular context, kissing interactions are important for tertiary folding and pseudoknot formation, whereas in a bimolecular context, they provide a basis for molecular recognition. In some cases, kissing complexes can be a prelude to strand displacement reactions where the two hairpins resolve to form a stable extended intermolecular duplex. The kinetics and thermodynamics of kissing-complex formation and their subsequent strand-displacement reactions are poorly understood. Here, biophysical techniques including isothermal titration calorimetry, surface plasmon resonance, and single-molecule fluorescence have been employed to probe the factors that govern the stability of kissing complexes and their subsequent structural rearrangements. We show that the general understanding of RNA duplex formation can be extended to kissing complexes but that kissing complexes display an unusual level of stability relative to simple duplexes of the same sequence. These interactions form and break many times at room temperature before becoming committed to a slow, irreversible forward transition to the strand-displaced form. Furthermore, using smFRET we show that the primary difference between stable and labile kissing complexes is based almost completely on their off rates. Both stable and labile complexes form at the same rate within error, but less stable species dissociate rapidly, allowing us to understand how these complexes can help generate specificity along a folding pathway or during a gene regulation event.
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49
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Ge L, Vernon M, Simon S, Maham Y, Sjöblom J, Xu Z. Interactions of divalent cations with tetrameric acid aggregates in aqueous solutions. Colloids Surf A Physicochem Eng Asp 2012. [DOI: 10.1016/j.colsurfa.2011.12.074] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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50
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Feldmann EA, Ni S, Sahu ID, Mishler CH, Risser DD, Murakami JL, Tom SK, McCarrick RM, Lorigan GA, Tolbert BS, Callahan SM, Kennedy MA. Evidence for Direct Binding between HetR from Anabaena sp. PCC 7120 and PatS-5. Biochemistry 2011; 50:9212-24. [DOI: 10.1021/bi201226e] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Erik A. Feldmann
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Shuisong Ni
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Indra D. Sahu
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Clay H. Mishler
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Douglas D. Risser
- Department of Microbiology, University of Hawaii, Honolulu, Hawaii 96822, United
States
| | - Jodi L. Murakami
- Department of Microbiology, University of Hawaii, Honolulu, Hawaii 96822, United
States
| | - Sasa K. Tom
- Department of Microbiology, University of Hawaii, Honolulu, Hawaii 96822, United
States
| | - Robert M. McCarrick
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Gary A. Lorigan
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Blanton S. Tolbert
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
| | - Sean M. Callahan
- Department of Microbiology, University of Hawaii, Honolulu, Hawaii 96822, United
States
| | - Michael A. Kennedy
- Department of Chemistry and
Biochemistry, Miami University, Oxford,
Ohio 45056, United States
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