1
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Lu Y, Yang GZ, Yang D. Effects of ligand binding on dynamics of fatty acid binding protein and interactions with membranes. Biophys J 2022; 121:4024-4032. [PMID: 36196055 PMCID: PMC9675020 DOI: 10.1016/j.bpj.2022.09.043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 09/19/2022] [Accepted: 09/27/2022] [Indexed: 11/18/2022] Open
Abstract
Intracellular transport of fatty acids involves binding of ligands to their carrier fatty acid binding proteins (FABPs) and interactions of ligand-free and -bound FABPs with membranes. Previous studies focused on ligand-free FABPs. Here, our amide hydrogen exchange data showed that oleic acid binding to human intestinal FABP (hIFABP) stabilizes the protein, most likely through enhancing the hydrogen-bonding network, and induces rearrangement of sidechains even far away from the ligand binding site. Using NMR relaxation techniques, we found that the ligand binding affects not only conformational exchanges between major and minor states but also the affinity of hIFABP to nanodiscs. Analyses of the relaxation and amide exchange data suggested that two minor native-like states existing in both ligand-free and -bound hIFABPs originate from global "breathing" motions, while one minor native-like state comes from local motions. The amide hydrogen exchange data also indicated that helix αII undergoes local unfolding through which ligands can exit from the binding cavity.
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Affiliation(s)
- Yimei Lu
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Gabriel Zhang Yang
- Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, BC, Canada
| | - Daiwen Yang
- Department of Biological Sciences, National University of Singapore, Singapore.
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2
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Kandwal S, Fayne D. Repurposing drugs for treatment of SARS-CoV-2 infection: computational design insights into mechanisms of action. J Biomol Struct Dyn 2022; 40:1316-1330. [PMID: 32964805 PMCID: PMC7544922 DOI: 10.1080/07391102.2020.1825232] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 09/12/2020] [Indexed: 12/15/2022]
Abstract
The COVID-19 pandemic has negatively affected human life globally. It has led to economic crises and health emergencies across the world, spreading rapidly among the human population and has caused many deaths. Currently, there are no treatments available for COVID-19 so there is an urgent need to develop therapeutic interventions that could be used against the novel coronavirus infection. In this research, we used computational drug design technologies to repurpose existing drugs as inhibitors of SARS-CoV-2 viral proteins. The Broad Institute's Drug Repurposing Hub consists of in-development/approved drugs and was computationally screened to identify potential hits which could inhibit protein targets encoded by the SARS-CoV-2 genome. By virtually screening the Broad collection, using rationally designed pharmacophore features, we identified molecules which may be repurposed against viral nucleocapsid and non-structural proteins. The pharmacophore features were generated after careful visualisation of the interactions between co-crystalised ligands and the protein binding site. The ChEMBL database was used to determine the compound's level of inhibition of SARS-CoV-2 and correlate the predicted viral protein target with whole virus in vitro data. The results from this study may help to accelerate drug development against COVID-19 and the hit compounds should be progressed through further in vitro and in vivo studies on SARS-CoV-2.
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Affiliation(s)
- Shubhangi Kandwal
- Department of Clinical Medicine, Trinity Translational Medicine Institute, Trinity College Dublin, Dublin, Ireland
| | - Darren Fayne
- Molecular Design Group, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
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3
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Stamboroski S, Boateng K, Lierath J, Kowalik T, Thiel K, Köppen S, Noeske PLM, Brüggemann D. Influence of Divalent Metal Ions on the Precipitation of the Plasma Protein Fibrinogen. Biomacromolecules 2021; 22:4642-4658. [PMID: 34670087 DOI: 10.1021/acs.biomac.1c00930] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fibrinogen nanofibers are very attractive biomaterials to mimic the native blood clot architecture. Previously, we reported the self-assembly of fibrinogen nanofibers in the presence of monovalent salts and have now studied how divalent salts influence fibrinogen precipitation. Although the secondary fibrinogen structure was significantly altered with divalent metal ions, morphological analysis revealed exclusively smooth fibrinogen precipitates. In situ monitoring of the surface roughness facilitated predicting the tendency of various salts to form fibrinogen fibers or smooth films. Analysis of the chemical composition revealed that divalent salts were removed from smooth fibrinogen films upon rinsing while monovalent Na+ species were still present in fibrinogen fibers. Therefore, we assume that the decisive factor controlling the morphology of fibrinogen precipitates is direct ion-protein contact, which requires disruption of the ion-surrounding hydration shells. We conclude that in fibrinogen aggregates, this mechanism is effective only for monovalent ions, whereas divalent ions are limited to indirect fibrinogen adsorption.
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Affiliation(s)
- Stephani Stamboroski
- Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Strasse 12, 28359 Bremen, Germany.,Institute for Biophysics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
| | - Kwasi Boateng
- Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Strasse 12, 28359 Bremen, Germany.,Institute for Biophysics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
| | - Jana Lierath
- Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Strasse 12, 28359 Bremen, Germany.,Institute for Biophysics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
| | - Thomas Kowalik
- Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Strasse 12, 28359 Bremen, Germany
| | - Karsten Thiel
- Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Strasse 12, 28359 Bremen, Germany
| | - Susan Köppen
- Hybrid Materials Interfaces Group, Faculty of Production Engineering and Bremen Center for Computational Materials Science, University of Bremen, Am Fallturm 1, 28359 Bremen, Germany.,MAPEX Center for Materials and Processes, University of Bremen, 28359 Bremen, Germany
| | - Paul-Ludwig Michael Noeske
- Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Strasse 12, 28359 Bremen, Germany
| | - Dorothea Brüggemann
- Institute for Biophysics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany.,MAPEX Center for Materials and Processes, University of Bremen, 28359 Bremen, Germany
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4
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Lu Y, Yang D. Conformational exchange of fatty acid binding protein induced by protein-nanodisc interactions. Biophys J 2021; 120:4672-4681. [PMID: 34600898 DOI: 10.1016/j.bpj.2021.09.037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 08/20/2021] [Accepted: 09/28/2021] [Indexed: 10/20/2022] Open
Abstract
Fatty acid binding proteins (FABPs) can facilitate the transfer of long-chain fatty acids between intracellular membranes across considerable distances. The transfer process involves fatty acids, their donor membrane and acceptor membrane, and FABPs, implying that potential protein-membrane interactions exist. Despite intensive studies on FABP-membrane interactions, the interaction mode remains elusive, and the protein-membrane association and dissociation rates are inconsistent. In this study, we used nanodiscs (NDs) as mimetic membranes to investigate FABP-membrane interactions. Our NMR experiments showed that human intestinal FABP interacts weakly with both negatively charged and neutral membranes, but it prefers the negatively charged one. Through simultaneous analysis of NMR relaxation in the rotating-frame (R1ρ), relaxation dispersion, chemical exchange saturation transfer, and dark-state exchange saturation transfer data, we estimated the affinity of the protein to negatively charged NDs, the dissociation rate, and apparent association rate. We further showed that the protein in the ND-bound state adopts a conformation different from the native structure and the second helix is very likely involved in interactions with NDs. We also found a membrane-induced FABP conformational state that exists only in the presence of NDs. This state is native-like, different from other conformational states in structure, unbound to NDs, and in dynamic equilibrium with the ND-bound state.
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Affiliation(s)
- Yimei Lu
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Daiwen Yang
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
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5
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Katti S, Igumenova TI. Interference of pH buffer with Pb 2+-peripheral domain interactions: obstacle or opportunity? Metallomics 2020; 12:164-172. [PMID: 32051983 DOI: 10.1039/d0mt00002g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Pb2+ is a xenobiotic metal ion that competes for Ca2+-binding sites in proteins. Using the peripheral Ca2+-sensing domains of Syt1, we show that the chelating pH buffer Bis-Tris enables identification and functional characterization of high-affinity Pb2+ sites that are likely to be targeted by bioavailable Pb2+.
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Affiliation(s)
- Sachin Katti
- Department of Biochemistry and Biophysics, Texas A&M University, 300 Olsen Boulevard, College Station, TX 77843, USA.
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6
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Wiezel GA, Rustiguel JK, Morgenstern D, Zoccal KF, Faccioli LH, Nonato MC, Ueberheide B, Arantes EC. Insights into the structure, function and stability of bordonein-L, the first L-amino acid oxidase from Crotalus durissus terrificus snake venom. Biochimie 2019; 163:33-49. [DOI: 10.1016/j.biochi.2019.05.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 05/06/2019] [Indexed: 01/18/2023]
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7
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Cheng P, Liu D, Chee PX, Yang D, Long D. Atomistic Insights into the Functional Instability of the Second Helix of Fatty Acid Binding Protein. Biophys J 2019; 117:239-246. [PMID: 31301805 DOI: 10.1016/j.bpj.2019.06.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 05/19/2019] [Accepted: 06/13/2019] [Indexed: 12/21/2022] Open
Abstract
Structural dynamics of fatty acid binding proteins (FABPs), which accommodate poorly soluble ligands in the internalized binding cavities, are intimately related to their function. Recently, local unfolding of the α-helical cap in a variant of human intestinal FABP (IFABP) has been shown to correlate with the kinetics of ligand association, shedding light on the nature of the critical conformational reorganization. Yet, the physical origin and mechanism of the functionally relevant transient unfolding remain elusive. Here, we investigate the intrinsic structural instability of the second helix (αII) of IFABP in comparison with other segments of the protein using hydrogen-exchange NMR spectroscopy, microsecond molecular dynamics simulations, and enhanced sampling techniques. Although tertiary interactions positively contribute to the stability of helices in IFABP, the intrinsic unfolding tendency of αII is encoded in its primary sequence and can be described by the Lifson-Roig theory in the absence of tertiary interactions. The unfolding pathway of αII in intact proteins involves an on-pathway intermediate state that is characterized with the fraying of the last helical turn, captured by independent enhanced sampling methods. The simulations in this work, combined with hydrogen-exchange NMR data, provide new, to our knowledge, atomistic insights into the functional local unfolding of FABPs.
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Affiliation(s)
- Peng Cheng
- Hefei National Laboratory for Physical Sciences at the Microscale & School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Dan Liu
- Hefei National Laboratory for Physical Sciences at the Microscale & School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Pin Xuan Chee
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Daiwen Yang
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Dong Long
- Hefei National Laboratory for Physical Sciences at the Microscale & School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China; Department of Chemistry, University of Science and Technology of China, Hefei, Anhui, China.
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8
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Martin GG, Huang H, McIntosh AL, Kier AB, Schroeder F. Endocannabinoid Interaction with Human FABP1: Impact of the T94A Variant. Biochemistry 2017; 56:5147-5159. [DOI: 10.1021/acs.biochem.7b00647] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Gregory G. Martin
- Department of Physiology and Pharmacology, Texas A&M University, College Station, Texas 77843-4466, United States
| | - Huan Huang
- Department of Physiology and Pharmacology, Texas A&M University, College Station, Texas 77843-4466, United States
| | - Avery L. McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, College Station, Texas 77843-4466, United States
| | - Ann B. Kier
- Department of Pathobiology, Texas A&M University, College Station, Texas 77843-4467, United States
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, College Station, Texas 77843-4466, United States
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9
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Konermann L. Addressing a Common Misconception: Ammonium Acetate as Neutral pH "Buffer" for Native Electrospray Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:1827-1835. [PMID: 28710594 DOI: 10.1007/s13361-017-1739-3] [Citation(s) in RCA: 146] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 06/14/2017] [Accepted: 06/15/2017] [Indexed: 05/12/2023]
Abstract
Native ESI-MS involves the transfer of intact proteins and biomolecular complexes from solution into the gas phase. One potential pitfall is the occurrence of pH-induced changes that can affect the analyte while it is still surrounded by solvent. Most native ESI-MS studies employ neutral aqueous ammonium acetate solutions. It is a widely perpetuated misconception that ammonium acetate buffers the analyte solution at neutral pH. By definition, a buffer consists of a weak acid and its conjugate weak base. The buffering range covers the weak acid pKa ± 1 pH unit. NH4+ and CH3-COO- are not a conjugate acid/base pair, which means that they do not constitute a buffer at pH 7. Dissolution of ammonium acetate salt in water results in pH 7, but this pH is highly labile. Ammonium acetate does provide buffering around pH 4.75 (the pKa of acetic acid) and around pH 9.25 (the pKa of ammonium). This implies that neutral ammonium acetate solutions electrosprayed in positive ion mode will likely undergo acidification down to pH 4.75 ± 1 in the ESI plume. Ammonium acetate nonetheless remains a useful additive for native ESI-MS. It is a volatile electrolyte that can mimic the solvation properties experienced by proteins under physiological conditions. Also, a drop from pH 7 to around pH 4.75 is less dramatic than the acidification that would take place in pure water. It is hoped that the habit of referring to pH 7 solutions as ammonium acetate "buffer" will disappear from the literature. Ammonium acetate "solution" should be used instead. Graphical Abstract ᅟ.
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Affiliation(s)
- Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada.
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10
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Carson SD, Hafenstein S, Lee H. MOPS and coxsackievirus B3 stability. Virology 2016; 501:183-187. [PMID: 27940223 DOI: 10.1016/j.virol.2016.12.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 11/30/2016] [Accepted: 12/02/2016] [Indexed: 01/05/2023]
Abstract
Study of coxsackievirus B3 strain 28 (CVB3/28) stability using MOPS to improve buffering in the experimental medium revealed that MOPS (3-morpholinopropane-1-sulfonic acid) increased CVB3 stability and the effect was concentration dependent. Over the pH range 7.0-7.5, virus stability was affected by both pH and MOPS concentration. Computer-simulated molecular docking showed that MOPS can occupy the hydrophobic pocket in capsid protein VP1 where the sulfonic acid head group can form ionic and hydrogen bonds with Arg95 and Asn211 near the pocket opening. The effects of MOPS and hydrogen ion concentrations on the rate of virus decay were modeled by including corresponding parameters in a recent kinetic model. These results indicate that MOPS can directly associate with CVB3 and stabilize the virus, possibly by altering capsid conformational dynamics.
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Affiliation(s)
- Steven D Carson
- Department of Pathology and Microbiology University of Nebraska Medical Center, 986495 Nebraska Medical Center, Omaha, NE 68198-6495, USA.
| | - Susan Hafenstein
- Department of Medicine, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
| | - Hyunwook Lee
- Department of Medicine, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
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11
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Karki I, Christen MT, Spiriti J, Slack RL, Oda M, Kanaori K, Zuckerman DM, Ishima R. Entire-Dataset Analysis of NMR Fast-Exchange Titration Spectra: A Mg 2+ Titration Analysis for HIV-1 Ribonuclease H Domain. J Phys Chem B 2016; 120:12420-12431. [PMID: 27973819 DOI: 10.1021/acs.jpcb.6b08323] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This article communicates our study to elucidate the molecular determinants of weak Mg2+ interaction with the ribonuclease H (RNH) domain of HIV-1 reverse transcriptase in solution. As the interaction is weak (a ligand-dissociation constant >1 mM), nonspecific Mg2+ interaction with the protein or interaction of the protein with other solutes that are present in the buffer solution can confound the observed Mg2+-titration data. To investigate these indirect effects, we monitored changes in the chemical shifts of backbone amides of RNH by recording NMR 1H-15N heteronuclear single-quantum coherence spectra upon titration of Mg2+ into an RNH solution. We performed the titration under three different conditions: (1) in the absence of NaCl, (2) in the presence of 50 mM NaCl, and (3) at a constant 160 mM Cl- concentration. Careful analysis of these three sets of titration data, along with molecular dynamics simulation data of RNH with Na+ and Cl- ions, demonstrates two characteristic phenomena distinct from the specific Mg2+ interaction with the active site: (1) weak interaction of Mg2+, as a salt, with the substrate-handle region of the protein and (2) overall apparent lower Mg2+ affinity in the absence of NaCl compared to that in the presence of 50 mM NaCl. A possible explanation may be that the titrated MgCl2 is consumed as a salt and interacts with RNH in the absence of NaCl. In addition, our data suggest that Na+ increases the kinetic rate of the specific Mg2+ interaction at the active site of RNH. Taken together, our study provides biophysical insight into the mechanism of weak metal interaction on a protein.
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Affiliation(s)
- Ichhuk Karki
- Department of Structural Biology and ‡Department of Computational and Systems Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States.,Graduate School of Life and Environmental Sciences, Kyoto Prefectural University and ⊥Department of Biomolecular Engineering, Kyoto Institute of Technology , Kyoto 606, Japan
| | - Martin T Christen
- Department of Structural Biology and ‡Department of Computational and Systems Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States.,Graduate School of Life and Environmental Sciences, Kyoto Prefectural University and ⊥Department of Biomolecular Engineering, Kyoto Institute of Technology , Kyoto 606, Japan
| | - Justin Spiriti
- Department of Structural Biology and ‡Department of Computational and Systems Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States.,Graduate School of Life and Environmental Sciences, Kyoto Prefectural University and ⊥Department of Biomolecular Engineering, Kyoto Institute of Technology , Kyoto 606, Japan
| | - Ryan L Slack
- Department of Structural Biology and ‡Department of Computational and Systems Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States.,Graduate School of Life and Environmental Sciences, Kyoto Prefectural University and ⊥Department of Biomolecular Engineering, Kyoto Institute of Technology , Kyoto 606, Japan
| | - Masayuki Oda
- Department of Structural Biology and ‡Department of Computational and Systems Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States.,Graduate School of Life and Environmental Sciences, Kyoto Prefectural University and ⊥Department of Biomolecular Engineering, Kyoto Institute of Technology , Kyoto 606, Japan
| | - Kenji Kanaori
- Department of Structural Biology and ‡Department of Computational and Systems Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States.,Graduate School of Life and Environmental Sciences, Kyoto Prefectural University and ⊥Department of Biomolecular Engineering, Kyoto Institute of Technology , Kyoto 606, Japan
| | - Daniel M Zuckerman
- Department of Structural Biology and ‡Department of Computational and Systems Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States.,Graduate School of Life and Environmental Sciences, Kyoto Prefectural University and ⊥Department of Biomolecular Engineering, Kyoto Institute of Technology , Kyoto 606, Japan
| | - Rieko Ishima
- Department of Structural Biology and ‡Department of Computational and Systems Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States.,Graduate School of Life and Environmental Sciences, Kyoto Prefectural University and ⊥Department of Biomolecular Engineering, Kyoto Institute of Technology , Kyoto 606, Japan
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12
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Schroeder F, McIntosh AL, Martin GG, Huang H, Landrock D, Chung S, Landrock KK, Dangott LJ, Li S, Kaczocha M, Murphy EJ, Atshaves BP, Kier AB. Fatty Acid Binding Protein-1 (FABP1) and the Human FABP1 T94A Variant: Roles in the Endocannabinoid System and Dyslipidemias. Lipids 2016; 51:655-76. [PMID: 27117865 PMCID: PMC5408584 DOI: 10.1007/s11745-016-4155-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 04/11/2016] [Indexed: 01/01/2023]
Abstract
The first discovered member of the mammalian FABP family, liver fatty acid binding protein (FABP1, L-FABP), occurs at high cytosolic concentration in liver, intestine, and in the case of humans also in kidney. While the rat FABP1 is well studied, the extent these findings translate to human FABP1 is not clear-especially in view of recent studies showing that endocannabinoids and cannabinoids represent novel rat FABP1 ligands and FABP1 gene ablation impacts the hepatic endocannabinoid system, known to be involved in non-alcoholic fatty liver (NAFLD) development. Although not detectable in brain, FABP1 ablation nevertheless also impacts brain endocannabinoids. Despite overall tertiary structure similarity, human FABP1 differs significantly from rat FABP1 in secondary structure, much larger ligand binding cavity, and affinities/specificities for some ligands. Moreover, while both mouse and human FABP1 mediate ligand induction of peroxisome proliferator activated receptor-α (PPARα), they differ markedly in pattern of genes induced. This is critically important because a highly prevalent human single nucleotide polymorphism (SNP) (26-38 % minor allele frequency and 8.3 ± 1.9 % homozygous) results in a FABP1 T94A substitution that further accentuates these species differences. The human FABP1 T94A variant is associated with altered body mass index (BMI), clinical dyslipidemias (elevated plasma triglycerides and LDL cholesterol), atherothrombotic cerebral infarction, and non-alcoholic fatty liver disease (NAFLD). Resolving human FABP1 and the T94A variant's impact on the endocannabinoid and cannabinoid system is an exciting challenge due to the importance of this system in hepatic lipid accumulation as well as behavior, pain, inflammation, and satiety.
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Affiliation(s)
- Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA.
| | - Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Huan Huang
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Sarah Chung
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Kerstin K Landrock
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Lawrence J Dangott
- Department of Biochemistry and Biophysics, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Shengrong Li
- Avanti Polar Lipids, 700 Industrial Park Dr., Alabaster, AL, 35007-9105, USA
| | - Martin Kaczocha
- Department of Anesthesiology, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Eric J Murphy
- Department of Pharmacology, Physiology, and Therapeutics and Chemistry, University of North Dakota, Grand Forks, ND, 58202-9037, USA
| | - Barbara P Atshaves
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
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13
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Chen ASY, Westwood NJ, Brear P, Rogers GW, Mavridis L, Mitchell JBO. A Random Forest Model for Predicting Allosteric and Functional Sites on Proteins. Mol Inform 2016; 35:125-35. [DOI: 10.1002/minf.201500108] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 12/28/2015] [Indexed: 01/17/2023]
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14
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Abstract
Nucleic acid crystallization buffers contain a large variety of chemicals fitting specific needs. Among them, anions are often solely considered for pH-regulating purposes and as cationic co-salts while their ability to directly bind to nucleic acid structures is rarely taken into account. Here we review current knowledge related to the use of anions in crystallization buffers along with data on their biological prevalence. Chloride ions are frequently identified in crystal structures but display low cytosolic concentrations. Hence, they are thought to be distant from nucleic acid structures in the cell. Sulfate ions are also frequently identified in crystal structures but their localization in the cell remains elusive. Nevertheless, the characterization of the binding properties of these ions is essential for better interpreting the solvent structure in crystals and consequently, avoiding mislabeling of electron densities. Furthermore, understanding the binding properties of these anions should help to get clues related to their potential effects in crowded cellular environments.
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Affiliation(s)
- Luigi D'Ascenzo
- Architecture et Réactivité de l'ARN, Institut de Biologie Moléculaire et Cellulaire du CNRS, UPR 9002 CNRS/Université de Strasbourg, 15, rue René Descartes, Strasbourg Cedex, 67084, France
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15
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Jiang B, Yu B, Zhang X, Liu M, Yang D. A (15)N CPMG relaxation dispersion experiment more resistant to resonance offset and pulse imperfection. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 257:1-7. [PMID: 26037134 DOI: 10.1016/j.jmr.2015.05.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 05/04/2015] [Accepted: 05/05/2015] [Indexed: 06/04/2023]
Abstract
Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion is a powerful NMR method to study protein dynamics on the microsecond-millisecond time scale. J-coupling, resonance offset, radio frequency field inhomogeneity, and pulse imperfection often introduce systematic errors into the measured transverse relaxation rates. Here we proposed a modified continuous wave decoupling CPMG experiment, which is more unaffected by resonance offset and pulse imperfection. We found that it is unnecessary to match the decoupling field strength with the delay between CPMG refocusing pulses, provided that decoupling field is strong enough. The performance of the scheme proposed here was shown by simulations and further demonstrated experimentally on a fatty acid binding protein.
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Affiliation(s)
- Bin Jiang
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore; State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, The Chinese Academy of Sciences, 430071 Wuhan, China.
| | - Binhan Yu
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
| | - Xu Zhang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, The Chinese Academy of Sciences, 430071 Wuhan, China
| | - Maili Liu
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, The Chinese Academy of Sciences, 430071 Wuhan, China.
| | - Daiwen Yang
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore.
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16
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Abstract
Solution-state NMR has been widely applied to determine the three-dimensional structure, dynamics, and molecular interactions of proteins. The designs of experiments used in protein NMR differ from those used for small-molecule NMR, primarily because the information available prior to an experiment, such as molecular mass and knowledge of the primary structure, is unique for proteins compared to small molecules. In this review article, protein NMR for structural biology is introduced with comparisons to small-molecule NMR, such as descriptions of labeling strategies and the effects of molecular dynamics on relaxation. Next, applications for protein NMR are reviewed, especially practical aspects for protein-observed ligand-protein interaction studies. Overall, the following topics are described: (1) characteristics of protein NMR, (2) methods to detect protein-ligand interactions by NMR, and (3) practical aspects of carrying out protein-observed inhibitor-protein interaction studies.
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Affiliation(s)
- Rieko Ishima
- Address correspondence to Rieko Ishima: Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA; Tel: 412-648-9056; Fax: 412-648-9008;
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17
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Ferreira CMH, Pinto ISS, Soares EV, Soares HMVM. (Un)suitability of the use of pH buffers in biological, biochemical and environmental studies and their interaction with metal ions – a review. RSC Adv 2015. [DOI: 10.1039/c4ra15453c] [Citation(s) in RCA: 189] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The present work reviews, discusses and update the metal complexation characteristics of thirty one buffers commercially available. Additionally, their impact on the biological systems is also presented and discussed.
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Affiliation(s)
- Carlos M. H. Ferreira
- REQUIMTE/LAQV
- Department of Chemical Engineering
- Faculty of Engineering
- University of Porto
- Porto
| | - Isabel S. S. Pinto
- REQUIMTE/LAQV
- Department of Chemical Engineering
- Faculty of Engineering
- University of Porto
- Porto
| | - Eduardo V. Soares
- Bioengineering Laboratory
- Chemical Engineering Department
- ISEP-School of Engineering of Polytechnic Institute of Porto
- Porto
- Portugal
| | - Helena M. V. M. Soares
- REQUIMTE/LAQV
- Department of Chemical Engineering
- Faculty of Engineering
- University of Porto
- Porto
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18
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Ragona L, Pagano K, Tomaselli S, Favretto F, Ceccon A, Zanzoni S, D'Onofrio M, Assfalg M, Molinari H. The role of dynamics in modulating ligand exchange in intracellular lipid binding proteins. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:1268-78. [PMID: 24768771 DOI: 10.1016/j.bbapap.2014.04.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 04/14/2014] [Accepted: 04/16/2014] [Indexed: 11/29/2022]
Abstract
Lipids are essential for many biological processes and crucial in the pathogenesis of several diseases. Intracellular lipid-binding proteins (iLBPs) provide mobile hydrophobic binding sites that allow hydrophobic or amphipathic lipid molecules to penetrate into and across aqueous layers. Thus iLBPs mediate the lipid transport within the cell and participate to a spectrum of tissue-specific pathways involved in lipid homeostasis. Structural studies have shown that iLBPs' binding sites are inaccessible from the bulk, implying that substrate binding should involve a conformational change able to produce a ligand entry portal. Many studies have been reported in the last two decades on iLBPs indicating that their dynamics play a pivotal role in regulating ligand binding and targeted release. The ensemble of reported data has not been reviewed until today. This review is thus intended to summarize and possibly generalize the results up to now described, providing a picture which could help to identify the missing notions necessary to improve our understanding of the role of dynamics in iLBPs' molecular recognition. Such notions would clarify the chemistry of lipid binding to iLBPs and set the basis for the development of new drugs.
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Affiliation(s)
- Laura Ragona
- Laboratorio NMR, Istituto per lo Studio delle Macromolecole (ISMAC), CNR, Via Bassini 15, 20133 Milano, Italy
| | - Katiuscia Pagano
- Laboratorio NMR, Istituto per lo Studio delle Macromolecole (ISMAC), CNR, Via Bassini 15, 20133 Milano, Italy
| | - Simona Tomaselli
- Laboratorio NMR, Istituto per lo Studio delle Macromolecole (ISMAC), CNR, Via Bassini 15, 20133 Milano, Italy
| | - Filippo Favretto
- Dipartimento di Biotecnologie, Università degli Studi di Verona, Strada Le Grazie 15, 37134 Verona, Italy
| | - Alberto Ceccon
- Dipartimento di Biotecnologie, Università degli Studi di Verona, Strada Le Grazie 15, 37134 Verona, Italy
| | - Serena Zanzoni
- Dipartimento di Biotecnologie, Università degli Studi di Verona, Strada Le Grazie 15, 37134 Verona, Italy
| | - Mariapina D'Onofrio
- Dipartimento di Biotecnologie, Università degli Studi di Verona, Strada Le Grazie 15, 37134 Verona, Italy
| | - Michael Assfalg
- Dipartimento di Biotecnologie, Università degli Studi di Verona, Strada Le Grazie 15, 37134 Verona, Italy
| | - Henriette Molinari
- Laboratorio NMR, Istituto per lo Studio delle Macromolecole (ISMAC), CNR, Via Bassini 15, 20133 Milano, Italy.
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19
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Martin GG, McIntosh AL, Huang H, Gupta S, Atshaves BP, Landrock KK, Landrock D, Kier AB, Schroeder F. The human liver fatty acid binding protein T94A variant alters the structure, stability, and interaction with fibrates. Biochemistry 2013; 52:9347-57. [PMID: 24299557 PMCID: PMC3930105 DOI: 10.1021/bi401014k] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Although the human liver fatty acid binding protein (L-FABP) T94A variant arises from the most commonly occurring single-nucleotide polymorphism in the entire FABP family, there is a complete lack of understanding regarding the role of this polymorphism in human disease. It has been hypothesized that the T94A substitution results in the complete loss of ligand binding ability and function analogous to that seen with L-FABP gene ablation. This possibility was addressed using the recombinant human wild-type (WT) T94T and T94A variant L-FABP and cultured primary human hepatocytes. Nonconservative replacement of the medium-sized, polar, uncharged T residue with a smaller, nonpolar, aliphatic A residue at position 94 of the human L-FABP significantly increased the L-FABP α-helical structure content at the expense of β-sheet content and concomitantly decreased the thermal stability. T94A did not alter the binding affinities for peroxisome proliferator-activated receptor α (PPARα) agonist ligands (phytanic acid, fenofibrate, and fenofibric acid). While T94A did not alter the impact of phytanic acid and only slightly altered that of fenofibrate on the human L-FABP secondary structure, the active metabolite fenofibric acid altered the T94A secondary structure much more than that of the WT T94T L-FABP. Finally, in cultured primary human hepatocytes, the T94A variant exhibited a significantly reduced extent of fibrate-mediated induction of PPARα-regulated proteins such as L-FABP, FATP5, and PPARα itself. Thus, while the T94A substitution did not alter the affinity of the human L-FABP for PPARα agonist ligands, it significantly altered the human L-FABP structure, stability, and conformational and functional response to fibrate.
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Affiliation(s)
- Gregory G. Martin
- Department of Physiology and Pharmacology, Texas A&M University, TVMC College Station, TX 77843-4466
| | - Avery L. McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC College Station, TX 77843-4466
| | - Huan Huang
- Department of Physiology and Pharmacology, Texas A&M University, TVMC College Station, TX 77843-4466
| | - Shipra Gupta
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
| | - Barbara P. Atshaves
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
| | - Kerstin K. Landrock
- Department of Pathobiology, Texas A&M University, TVMC College Station, TX 77843-4467
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, TVMC College Station, TX 77843-4467
| | - Ann B. Kier
- Department of Pathobiology, Texas A&M University, TVMC College Station, TX 77843-4467
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC College Station, TX 77843-4466
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20
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Metrick MA, Temple JE, MacDonald G. The effects of buffers and pH on the thermal stability, unfolding and substrate binding of RecA. Biophys Chem 2013; 184:29-36. [DOI: 10.1016/j.bpc.2013.08.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 08/06/2013] [Accepted: 08/06/2013] [Indexed: 10/26/2022]
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21
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Wong M, Khirich G, Loria JP. Correction to What’s in Your Buffer? Solute Altered Millisecond Motions Detected by Solution NMR. Biochemistry 2013. [DOI: 10.1021/bi401247g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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22
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Inhibitors of Fatty Acid Synthesis Induce PPAR α -Regulated Fatty Acid β -Oxidative Genes: Synergistic Roles of L-FABP and Glucose. PPAR Res 2013; 2013:865604. [PMID: 23533380 PMCID: PMC3600304 DOI: 10.1155/2013/865604] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 12/21/2012] [Indexed: 12/21/2022] Open
Abstract
While TOFA (acetyl CoA carboxylase inhibitor) and C75 (fatty acid synthase inhibitor) prevent lipid accumulation by inhibiting fatty acid synthesis, the mechanism of action is not simply accounted for by inhibition of the enzymes alone.
Liver fatty acid binding protein (L-FABP), a mediator of long chain fatty acid signaling to peroxisome
proliferator-activated receptor-α (PPARα) in the nucleus, was found to bind
TOFA and its activated CoA thioester, TOFyl-CoA, with high affinity while binding C75 and C75-CoA
with lower affinity. Binding of TOFA and C75-CoA significantly altered L-FABP secondary structure. High (20 mM) but not physiological
(6 mM) glucose conferred on both TOFA and C75 the ability to induce PPARα transcription of the fatty
acid β-oxidative enzymes CPT1A, CPT2, and ACOX1 in cultured primary hepatocytes from wild-type (WT) mice.
However, L-FABP gene ablation abolished the effects of TOFA and C75 in the context of high glucose. These effects were not associated
with an increased cellular level of unesterified fatty acids but rather by increased intracellular glucose. These findings suggested that L-FABP may function as an intracellular fatty acid synthesis inhibitor binding protein
facilitating TOFA and C75-mediated induction of PPARα in the context of high glucose at levels similar to those in uncontrolled diabetes.
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23
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Cai J, Lücke C, Chen Z, Qiao Y, Klimtchuk E, Hamilton JA. Solution structure and backbone dynamics of human liver fatty acid binding protein: fatty acid binding revisited. Biophys J 2012; 102:2585-94. [PMID: 22713574 DOI: 10.1016/j.bpj.2012.04.039] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 04/10/2012] [Accepted: 04/10/2012] [Indexed: 12/21/2022] Open
Abstract
Liver fatty acid binding protein (L-FABP), a cytosolic protein most abundant in liver, is associated with intracellular transport of fatty acids, nuclear signaling, and regulation of intracellular lipolysis. Among the members of the intracellular lipid binding protein family, L-FABP is of particular interest as it can i), bind two fatty acid molecules simultaneously and ii), accommodate a variety of bulkier physiological ligands such as bilirubin and fatty acyl CoA. To better understand the promiscuous binding and transport properties of L-FABP, we investigated structure and dynamics of human L-FABP with and without bound ligands by means of heteronuclear NMR. The overall conformation of human L-FABP shows the typical β-clam motif. Binding of two oleic acid (OA) molecules does not alter the protein conformation substantially, but perturbs the chemical shift of certain backbone and side-chain protons that are involved in OA binding according to the structure of the human L-FABP/OA complex. Comparison of the human apo and holo L-FABP structures revealed no evidence for an "open-cap" conformation or a "swivel-back" mechanism of the K90 side chain upon ligand binding, as proposed for rat L-FABP. Instead, we postulate that the lipid binding process in L-FABP is associated with backbone dynamics.
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Affiliation(s)
- Jun Cai
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts, USA
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24
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Krause ME, Martin TT, Laurence JS. Mapping site-specific changes that affect stability of the N-terminal domain of calmodulin. Mol Pharm 2012; 9:734-43. [PMID: 22309490 DOI: 10.1021/mp2004109] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Biophysical tools have been invaluable in formulating therapeutic proteins. These tools characterize protein stability rapidly in a variety of solution conditions, but in general, the techniques lack the ability to discern site-specific information to probe how solution environment acts to stabilize or destabilize the protein. NMR spectroscopy can provide site-specific information about subtle structural changes of a protein under different conditions, enabling one to assess the mechanism of protein stabilization. In this study, NMR was employed to detect structural perturbations at individual residues as a result of altering pH and ionic strength. The N-terminal domain of calmodulin (N-CaM) was used as a model system, and the ¹H-¹⁵N heteronuclear single quantum coherence (HSQC) experiment was used to investigate effects of pH and ionic strength on individual residues. NMR analysis revealed that different solution conditions affect individual residues differently, even when the amino acid sequence and structure are highly similar. This study shows that addition of NMR to the formulation toolbox has the ability to extend understanding of the relationship between site-specific changes and overall protein stability.
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Affiliation(s)
- Mary E Krause
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas 66047, USA
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25
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Taha M, Gupta BS, Khoiroh I, Lee MJ. Interactions of Biological Buffers with Macromolecules: The Ubiquitous “Smart” Polymer PNIPAM and the Biological Buffers MES, MOPS, and MOPSO. Macromolecules 2011. [DOI: 10.1021/ma201790c] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mohamed Taha
- Department of Chemical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei 106-07, Taiwan
| | - Bhupender S. Gupta
- Department of Chemical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei 106-07, Taiwan
| | - Ianatul Khoiroh
- Department of Chemical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei 106-07, Taiwan
| | - Ming-Jer Lee
- Department of Chemical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei 106-07, Taiwan
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26
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Kameoka D, Ueda T, Imoto T. Effect of the Conformational Stability of the CH2 Domain on the Aggregation and Peptide Cleavage of a Humanized IgG. Appl Biochem Biotechnol 2011; 164:642-54. [DOI: 10.1007/s12010-011-9164-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Accepted: 01/10/2011] [Indexed: 12/01/2022]
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27
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Long D, Yang D. Millisecond timescale dynamics of human liver fatty acid binding protein: testing of its relevance to the ligand entry process. Biophys J 2010; 98:3054-61. [PMID: 20550918 DOI: 10.1016/j.bpj.2010.03.047] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2010] [Revised: 03/18/2010] [Accepted: 03/19/2010] [Indexed: 10/19/2022] Open
Abstract
For over a decade, scientists have been attempting to know more about the conformational dynamics of fatty acid binding proteins (FABPs), to answer the puzzling question of how ligands could access the internalized binding site(s). Conformational exchange of FABPs on the microsecond to millisecond timescales has been found in many FABPs and offers an important hypothesis for the ligand entry mechanism. Despite the potential significance, the validity of this hypothesis has not been verified yet. In this study, the slow dynamics of human liver fatty acid binding protein (hLFABP) that was shown previously to be highly flexible on millisecond timescales was quantitatively characterized in detail. In addition, the interaction between hLFABP and 1,8-ANS was studied using NMR spectroscopy, and the kinetic rate of ANS association to hLFABP was measured. We believe the current result excludes the possibility that the intrinsic millisecond dynamics of hLFABP represents a critical conformational reorganization process required for ligand entry, but implies that it may represent the exchange between the apo-state and a state resembling the singly-bound conformation. Furthermore, we suggest these results show that the ligand-entry related functional dynamics could occur on the microsecond/submicrosecond timescales, highly encouraging future computational studies on this topic.
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Affiliation(s)
- Dong Long
- Department of Biological Sciences, National University of Singapore, Singapore
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