1
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Anishkin A, Adepu KK, Bhandari D, Adams SH, Chintapalli SV. Computational Analysis Reveals Unique Binding Patterns of Oxygenated and Deoxygenated Myoglobin to the Outer Mitochondrial Membrane. Biomolecules 2023; 13:1138. [PMID: 37509174 PMCID: PMC10377724 DOI: 10.3390/biom13071138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 06/26/2023] [Accepted: 07/13/2023] [Indexed: 07/30/2023] Open
Abstract
Myoglobin (Mb) interaction with the outer mitochondrial membrane (OMM) promotes oxygen (O2) release. However, comprehensive molecular details on specific contact regions of the OMM with oxygenated (oxy-) and deoxygenated (deoxy-)Mb are missing. We used molecular dynamics (MD) simulations to explore the interaction of oxy- and deoxy-Mb with the membrane lipids of the OMM in two lipid compositions: (a) a typical whole membrane on average, and (b) specifically the cardiolipin-enriched cristae region (contact site). Unrestrained relaxations showed that on average, both the oxy- and deoxy-Mb established more stable contacts with the lipids typical of the cristae contact site, then with those of the average OMM. However, in steered detachment simulations, deoxy-Mb clung more tightly to the average OMM, and oxy-Mb strongly preferred the contact sites of the OMM. The MD simulation analysis further indicated that a non-specific binding, mediated by local electrostatic interactions, existed between charged or polar groups of Mb and the membrane, for stable interaction. To the best of our knowledge, this is the first computational study providing the molecular details of the direct Mb-mitochondria interaction that assisted in distinguishing the preferred localization of oxy- and deoxy-Mb on the OMM. Our findings support the existing experimental evidence on Mb-mitochondrial association and shed more insights on Mb-mediated O2 transport for cellular bioenergetics.
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Affiliation(s)
- Andriy Anishkin
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Kiran Kumar Adepu
- Arkansas Children's Nutrition Center, Little Rock, AR 72202, USA
- Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | | | - Sean H Adams
- Department of Surgery, School of Medicine, University of California Davis, Sacramento, CA 95616, USA
- Center for Alimentary and Metabolic Science, University of California Davis, Sacramento, CA 95616, USA
| | - Sree V Chintapalli
- Arkansas Children's Nutrition Center, Little Rock, AR 72202, USA
- Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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2
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Bringas M, Lombardi LE, Luque FJ, Estrin DA, Capece L. Ligand Binding Rate Constants in Heme Proteins Using Markov State Models and Molecular Dynamics Simulations. Chemphyschem 2019; 20:2451-2460. [PMID: 31365183 DOI: 10.1002/cphc.201900589] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 07/30/2019] [Indexed: 11/07/2022]
Abstract
Computer simulation studies of the molecular basis for ligand migration in proteins allow the description of key events such as the transition between docking sites, displacement of existing ligands and solvent molecules, and open/closure of specific "gates", among others. In heme proteins, ligand migration from the solvent to the active site preludes the binding to the heme iron and triggers different functions. In this work, molecular dynamics simulations, a Markov State Model of migration and empirical kinetic equations are combined to study the migration of O2 and NO in two truncated hemoglobins of Mycobacterium tuberculosis (Mt-TrHbN and Mt-TrHbO). For Mt-TrHbN, we show that the difference in the association constant in the oxy and deoxy states relies mainly in the displacement of water molecules anchored in the distal cavity in the deoxy form. The results here provide a valuable approach to study ligand migration in globins.
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Affiliation(s)
- Mauro Bringas
- Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina.,Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE-CONICET), C1428EGA, Buenos Aires, Argentina
| | - Leandro E Lombardi
- Instituto de Cálculo, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires - CONICET, C1428EGA, Buenos Aires, Argentina
| | - F Javier Luque
- Department of Nutrition, Food Sciences and Gastronomy, Faculty of Pharmacy and Food Sciences, University of Barcelona, Campus Torribera, 08921, Santa Coloma de Gramenet, Spain.,Institute of Biomedicine (IBUB) and Institute of Theoretical and Computational Chemistry (IQTCUB), University of Barcelona, 08028, Barcelona, Spain
| | - Darío A Estrin
- Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina.,Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE-CONICET), C1428EGA, Buenos Aires, Argentina
| | - Luciana Capece
- Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina.,Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE-CONICET), C1428EGA, Buenos Aires, Argentina
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3
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Johnson EA, Russo MM, Nye DB, Schlessman JL, Lecomte JTJ. Lysine as a heme iron ligand: A property common to three truncated hemoglobins from Chlamydomonas reinhardtii. Biochim Biophys Acta Gen Subj 2018; 1862:2660-2673. [PMID: 30251657 DOI: 10.1016/j.bbagen.2018.08.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 08/06/2018] [Accepted: 08/08/2018] [Indexed: 12/20/2022]
Abstract
BACKGROUND The nuclear genome of Chlamydomonas reinhardtii encodes a dozen hemoglobins of the truncated lineage. Four of these, named THB1-4, contain a single ~130-residue globin unit. THB1, which is cytoplasmic and capable of nitric oxide dioxygenation activity, uses a histidine and a lysine as axial ligands to the heme iron. In the present report, we compared THB2, THB3, and THB4 to THB1 to gain structural and functional insights into algal globins. METHODS We inspected properties of the globin domains prepared by recombinant means through site-directed mutagenesis, electronic absorption, CD, and NMR spectroscopies, and X-ray crystallography. RESULTS Recombinant THB3, which lacks the proximal histidine but has a distal histidine, binds heme weakly. NMR data demonstrate that the recombinant domains of THB2 and THB4 coordinate the ferrous heme iron with the proximal histidine and a lysine from the distal helix. An X-ray structure of ferric THB4 confirms lysine coordination. THB1, THB2, and THB4 have reduction potentials between -65 and -100 mV, are capable of nitric oxide dioxygenation, are reduced at different rates by the diaphorase domain of C. reinhardtii nitrate reductase, and show different response to peroxide treatment. CONCLUSIONS Three single-domain C. reinhardtii hemoglobins use lysine as a distal heme ligand in both Fe(III) and Fe(II) oxidation states. This common feature is likely related to enzymatic activity in the management of reactive oxygen species. GENERAL SIGNIFICANCE Primary structure analysis of hemoglobins has limited power in the prediction of heme ligation. Experimental determination reveals variations in this essential property across the superfamily.
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Affiliation(s)
- Eric A Johnson
- T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, United States
| | - Miranda M Russo
- T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, United States
| | - Dillon B Nye
- T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, United States
| | - Jamie L Schlessman
- Chemistry Department, U.S. Naval Academy, Annapolis, MD 21402, United States
| | - Juliette T J Lecomte
- T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, United States.
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4
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Chintapalli SV, Anishkin A, Adams SH. Exploring the entry route of palmitic acid and palmitoylcarnitine into myoglobin. Arch Biochem Biophys 2018; 655:56-66. [PMID: 30092229 DOI: 10.1016/j.abb.2018.07.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 07/23/2018] [Accepted: 07/31/2018] [Indexed: 11/26/2022]
Abstract
Myoglobin, besides its role in oxygen turnover, has gained recognition as a potential regulator of lipid metabolism. Previously, we confirmed the interaction of fatty acids and acylcarnitines with Oxy-Myoglobin, using both molecular dynamic simulations and Isothermal Titration Calorimetry studies. However, those studies were limited to testing only the binding sites derived from homology to fatty acid binding proteins and predictions using automated docking. To explore the entry mechanisms of the lipid ligands into myoglobin, we conducted molecular dynamic simulations of murine Oxy- and Deoxy-Mb structures with palmitate or palmitoylcarnitine starting at different positions near the protein surface. The simulations indicated that both ligands readily (under ∼10-20 ns) enter the Oxy-Mb structure through a dynamic area ("portal region") near heme, known to be the entry point for small molecule gaseous ligands like O2, CO and NO. The entry is not observed with Deoxy-Mb where lipid ligands move away from protein surface, due to a compaction of the entry portal and the heme-containing crevice in the Mb protein upon O2 removal. The results suggest quick spontaneous binding of lipids to Mb driven by hydrophobic interactions, strongly enhanced by oxygenation, and consistent with the emergent role of Mb in lipid metabolism.
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Affiliation(s)
- Sree V Chintapalli
- Arkansas Children's Nutrition Center -and- Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, USA.
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, USA
| | - Sean H Adams
- Arkansas Children's Nutrition Center -and- Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, USA
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5
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Mahinthichaichan P, Gennis RB, Tajkhorshid E. Cytochrome aa 3 Oxygen Reductase Utilizes the Tunnel Observed in the Crystal Structures To Deliver O 2 for Catalysis. Biochemistry 2018; 57:2150-2161. [PMID: 29546752 DOI: 10.1021/acs.biochem.7b01194] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cytochrome aa3 is the terminal respiratory enzyme of all eukaryotes and many bacteria and archaea, reducing O2 to water and harnessing the free energy from the reaction to generate the transmembrane electrochemical potential. The diffusion of O2 to the heme-copper catalytic site, which is buried deep inside the enzyme, is the initiation step of the reaction chemistry. Our previous molecular dynamics (MD) study with cytochrome ba3, a homologous enzyme of cytochrome aa3 in Thermus thermophilus, demonstrated that O2 diffuses from the lipid bilayer to its reduction site through a 25 Å long tunnel inferred by Xe binding sites detected by X-ray crystallography [Mahinthichaichan, P., Gennis, R., and Tajkhorshid, E. (2016) Biochemistry 55, 1265-1278]. Although a similar tunnel is observed in cytochrome aa3, this putative pathway appears partially occluded between the entrances and the reduction site. Also, the experimentally determined second-order rate constant for O2 delivery in cytochrome aa3 (∼108 M-1 s-1) is 10 times slower than that in cytochrome ba3 (∼109 M-1 s-1). A question to be addressed is whether cytochrome aa3 utilizes this X-ray-inferred tunnel as the primary pathway for O2 delivery. Using complementary computational methods, including multiple independent flooding MD simulations and implicit ligand sampling calculations, we probe the O2 delivery pathways in cytochrome aa3 of Rhodobacter sphaeroides. All of the O2 molecules that arrived in the reduction site during the simulations were found to diffuse through the X-ray-observed tunnel, despite its apparent constriction, supporting its role as the main O2 delivery pathway in cytochrome aa3. The rate constant for O2 delivery in cytochrome aa3, approximated using the simulation results, is 10 times slower than in cytochrome ba3, in agreement with the experimentally determined rate constants.
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Affiliation(s)
- Paween Mahinthichaichan
- Department of Biochemistry, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Robert B Gennis
- Department of Biochemistry , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Emad Tajkhorshid
- Department of Biochemistry, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
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6
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El Hage K, Mondal P, Meuwly M. Free energy simulations for protein ligand binding and stability. MOLECULAR SIMULATION 2018. [DOI: 10.1080/08927022.2017.1416115] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Krystel El Hage
- Department of Chemistry, University of Basel , Basel, Switzerland
| | - Padmabati Mondal
- Department of Chemistry, University of Basel , Basel, Switzerland
| | - Markus Meuwly
- Department of Chemistry, University of Basel , Basel, Switzerland
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7
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Carabet LA, Guertin M, Lagüe P, Lamoureux G. Mechanism of the Nitric Oxide Dioxygenase Reaction of Mycobacterium tuberculosis Hemoglobin N. J Phys Chem B 2017; 121:8706-8718. [DOI: 10.1021/acs.jpcb.7b06494] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Lavinia A. Carabet
- Department of Chemistry
and Biochemistry and Centre for Research in Molecular
Modeling (CERMM), Concordia University, Montréal, Québec, Canada H4B 1R6
| | | | | | - Guillaume Lamoureux
- Department of Chemistry
and Biochemistry and Centre for Research in Molecular
Modeling (CERMM), Concordia University, Montréal, Québec, Canada H4B 1R6
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8
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Koebke KJ, Waletzko MT, Pacheco AA. Direct Monitoring of the Reaction between Photochemically Generated Nitric Oxide and Mycobacterium tuberculosis Truncated Hemoglobin N Wild Type and Variant Forms: An Assessment of Computational Mechanistic Predictions. Biochemistry 2016; 55:686-96. [DOI: 10.1021/acs.biochem.5b01145] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Karl J. Koebke
- Department of Chemistry and
Biochemistry, University of Wisconsin—Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - Michael T. Waletzko
- Department of Chemistry and
Biochemistry, University of Wisconsin—Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - A. Andrew Pacheco
- Department of Chemistry and
Biochemistry, University of Wisconsin—Milwaukee, Milwaukee, Wisconsin 53211, United States
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9
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Hospital A, Goñi JR, Orozco M, Gelpí JL. Molecular dynamics simulations: advances and applications. Adv Appl Bioinform Chem 2015; 8:37-47. [PMID: 26604800 PMCID: PMC4655909 DOI: 10.2147/aabc.s70333] [Citation(s) in RCA: 233] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Molecular dynamics simulations have evolved into a mature technique that can be used effectively to understand macromolecular structure-to-function relationships. Present simulation times are close to biologically relevant ones. Information gathered about the dynamic properties of macromolecules is rich enough to shift the usual paradigm of structural bioinformatics from studying single structures to analyze conformational ensembles. Here, we describe the foundations of molecular dynamics and the improvements made in the direction of getting such ensemble. Specific application of the technique to three main issues (allosteric regulation, docking, and structure refinement) is discussed.
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Affiliation(s)
- Adam Hospital
- Institute for Research in Biomedicine, The Barcelona Institute of Science and Technology, University of Barcelona, Barcelona, Spain
| | - Josep Ramon Goñi
- Joint BSC-IRB Research Program in Computational Biology, University of Barcelona, Barcelona, Spain ; Barcelona Supercomputing Center, University of Barcelona, Barcelona, Spain
| | - Modesto Orozco
- Institute for Research in Biomedicine, The Barcelona Institute of Science and Technology, University of Barcelona, Barcelona, Spain ; Joint BSC-IRB Research Program in Computational Biology, University of Barcelona, Barcelona, Spain ; Barcelona Supercomputing Center, University of Barcelona, Barcelona, Spain ; Department of Biochemistry and Molecular Biology, University of Barcelona, Barcelona, Spain
| | - Josep L Gelpí
- Joint BSC-IRB Research Program in Computational Biology, University of Barcelona, Barcelona, Spain ; Barcelona Supercomputing Center, University of Barcelona, Barcelona, Spain ; Department of Biochemistry and Molecular Biology, University of Barcelona, Barcelona, Spain
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10
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Pesce A, Bustamante JP, Bidon-Chanal A, Boechi L, Estrin DA, Luque FJ, Sebilo A, Guertin M, Bolognesi M, Ascenzi P, Nardini M. The N-terminal pre-A region of Mycobacterium tuberculosis 2/2HbN promotes NO-dioxygenase activity. FEBS J 2015; 283:305-22. [PMID: 26499089 DOI: 10.1111/febs.13571] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 08/09/2015] [Accepted: 08/16/2015] [Indexed: 01/24/2023]
Abstract
UNLABELLED A unique defense mechanisms by which Mycobacterium tuberculosis protects itself from nitrosative stress is based on the O2 -dependent NO-dioxygenase (NOD) activity of truncated hemoglobin 2/2HbN (Mt2/2HbN). The NOD activity largely depends on the efficiency of ligand migration to the heme cavity through a two-tunnel (long and short) system; recently, it was also correlated with the presence at the Mt2/2HbN N-terminus of a short pre-A region, not conserved in most 2/2HbNs, whose deletion results in a drastic reduction of NO scavenging. In the present study, we report the crystal structure of Mt2/2HbN-ΔpreA, lacking the pre-A region, at a resolution of 1.53 Å. We show that removal of the pre-A region results in long range effects on the protein C-terminus, promoting the assembly of a stable dimer, both in the crystals and in solution. In the Mt2/2HbN-ΔpreA dimer, access of heme ligands to the short tunnel is hindered. Molecular dynamics simulations show that the long tunnel branch is the only accessible pathway for O2 -ligand migration to/from the heme, and that the gating residue Phe(62)E15 partly restricts the diameter of the tunnel. Accordingly, kinetic measurements indicate that the kon value for peroxynitrite isomerization by Mt2/2HbN-ΔpreA-Fe(III) is four-fold lower relative to the full-length protein, and that NO scavenging by Mt2/2HbN-ΔpreA-Fe(II)-O2 is reduced by 35-fold. Therefore, we speculate that Mt2/2HbN evolved to host the pre-A region as a mechanism for preventing dimerization, thus reinforcing the survival of the microorganism against the reactive nitrosative stress in macrophages. DATABASE Coordinates and structure factors have been deposited in the Protein Data Bank under accession number 5AB8.
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Affiliation(s)
| | - Juan P Bustamante
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, University of Buenos Aires, Argentina
| | - Axel Bidon-Chanal
- Departament de Fisicoquímica and Institut de Biomedicina (IBUB), Facultat de Farmàcia, University of Barcelona, Santa Coloma de Gramenet, Spain
| | - Leonardo Boechi
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, University of Buenos Aires, Argentina
| | - Darío A Estrin
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, University of Buenos Aires, Argentina
| | - Francisco Javier Luque
- Departament de Fisicoquímica and Institut de Biomedicina (IBUB), Facultat de Farmàcia, University of Barcelona, Santa Coloma de Gramenet, Spain
| | - Anne Sebilo
- Department of Biochemistry, Microbiology and Bioinformatics, Laval University, Quebec, Canada
| | - Michel Guertin
- Department of Biochemistry, Microbiology and Bioinformatics, Laval University, Quebec, Canada
| | - Martino Bolognesi
- Department of Biosciences, University of Milan, Italy.,CNR-IBF and CIMAINA, University of Milan, Italy
| | - Paolo Ascenzi
- Interdepartmental Laboratory of Electron Microscopy, Roma Tre University, Rome, Italy.,National Institute of Biostructures and Biosystems, Rome, Italy
| | - Marco Nardini
- Department of Biosciences, University of Milan, Italy
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11
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Cazade PA, Zheng W, Prada-Gracia D, Berezovska G, Rao F, Clementi C, Meuwly M. A comparative analysis of clustering algorithms: O2 migration in truncated hemoglobin I from transition networks. J Chem Phys 2015; 142:025103. [PMID: 25591387 DOI: 10.1063/1.4904431] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The ligand migration network for O2-diffusion in truncated Hemoglobin N is analyzed based on three different clustering schemes. For coordinate-based clustering, the conventional k-means and the kinetics-based Markov Clustering (MCL) methods are employed, whereas the locally scaled diffusion map (LSDMap) method is a collective-variable-based approach. It is found that all three methods agree well in their geometrical definition of the most important docking site, and all experimentally known docking sites are recovered by all three methods. Also, for most of the states, their population coincides quite favourably, whereas the kinetics of and between the states differs. One of the major differences between k-means and MCL clustering on the one hand and LSDMap on the other is that the latter finds one large primary cluster containing the Xe1a, IS1, and ENT states. This is related to the fact that the motion within the state occurs on similar time scales, whereas structurally the state is found to be quite diverse. In agreement with previous explicit atomistic simulations, the Xe3 pocket is found to be a highly dynamical site which points to its potential role as a hub in the network. This is also highlighted in the fact that LSDMap cannot identify this state. First passage time distributions from MCL clusterings using a one- (ligand-position) and two-dimensional (ligand-position and protein-structure) descriptor suggest that ligand- and protein-motions are coupled. The benefits and drawbacks of the three methods are discussed in a comparative fashion and highlight that depending on the questions at hand the best-performing method for a particular data set may differ.
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Affiliation(s)
- Pierre-André Cazade
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Wenwei Zheng
- Department of Chemistry, Rice University, 6100 Main St., Houston, Texas 77005, USA
| | - Diego Prada-Gracia
- School of Soft Matter Research, Freiburg Institute for Advanced Studies, Albertstrasse 19, 79104 Freiburg im Breisgau, Germany
| | - Ganna Berezovska
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Francesco Rao
- School of Soft Matter Research, Freiburg Institute for Advanced Studies, Albertstrasse 19, 79104 Freiburg im Breisgau, Germany
| | - Cecilia Clementi
- Department of Chemistry, Rice University, 6100 Main St., Houston, Texas 77005, USA
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
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12
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Chintapalli SV, Bhardwaj G, Patel R, Shah N, Patterson RL, van Rossum DB, Anishkin A, Adams SH. Molecular dynamic simulations reveal the structural determinants of Fatty Acid binding to oxy-myoglobin. PLoS One 2015; 10:e0128496. [PMID: 26030763 PMCID: PMC4451517 DOI: 10.1371/journal.pone.0128496] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 04/27/2015] [Indexed: 11/18/2022] Open
Abstract
The mechanism(s) by which fatty acids are sequestered and transported in muscle have not been fully elucidated. A potential key player in this process is the protein myoglobin (Mb). Indeed, there is a catalogue of empirical evidence supporting direct interaction of globins with fatty acid metabolites; however, the binding pocket and regulation of the interaction remains to be established. In this study, we employed a computational strategy to elucidate the structural determinants of fatty acids (palmitic & oleic acid) binding to Mb. Sequence analysis and docking simulations with a horse (Equus caballus) structural Mb reference reveals a fatty acid-binding site in the hydrophobic cleft near the heme region in Mb. Both palmitic acid and oleic acid attain a "U" shaped structure similar to their conformation in pockets of other fatty acid-binding proteins. Specifically, we found that the carboxyl head group of palmitic acid coordinates with the amino group of Lys45, whereas the carboxyl group of oleic acid coordinates with both the amino groups of Lys45 and Lys63. The alkyl tails of both fatty acids are supported by surrounding hydrophobic residues Leu29, Leu32, Phe33, Phe43, Phe46, Val67, Val68 and Ile107. In the saturated palmitic acid, the hydrophobic tail moves freely and occasionally penetrates deeper inside the hydrophobic cleft, making additional contacts with Val28, Leu69, Leu72 and Ile111. Our simulations reveal a dynamic and stable binding pocket in which the oxygen molecule and heme group in Mb are required for additional hydrophobic interactions. Taken together, these findings support a mechanism in which Mb acts as a muscle transporter for fatty acid when it is in the oxygenated state and releases fatty acid when Mb converts to deoxygenated state.
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Affiliation(s)
- Sree V. Chintapalli
- Arkansas Children’s Nutrition Center, and Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
- * E-mail: (SVC); (SHA)
| | - Gaurav Bhardwaj
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Davis, California, United States of America
| | - Reema Patel
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Davis, California, United States of America
- Department of Physiology and Membrane Biology, School of Medicine, University of California Davis, Davis, California, United States of America
| | - Natasha Shah
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Davis, California, United States of America
- Department of Physiology and Membrane Biology, School of Medicine, University of California Davis, Davis, California, United States of America
| | - Randen L. Patterson
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Davis, California, United States of America
- Department of Physiology and Membrane Biology, School of Medicine, University of California Davis, Davis, California, United States of America
| | - Damian B. van Rossum
- Center for Computational Proteomics, The Pennsylvania State University, State College, Pennsylvania, United States of America
- Department of Biology, The Pennsylvania State University, State College, Pennsylvania, United States of America
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, Maryland, United States of America
| | - Sean H. Adams
- Arkansas Children’s Nutrition Center, and Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
- * E-mail: (SVC); (SHA)
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13
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Rhéault JF, Gagné È, Guertin M, Lamoureux G, Auger M, Lagüe P. Molecular Model of Hemoglobin N from Mycobacterium tuberculosis Bound to Lipid Bilayers: A Combined Spectroscopic and Computational Study. Biochemistry 2015; 54:2073-84. [DOI: 10.1021/bi5010624] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Jean-François Rhéault
- Department
of Biochemistry, Microbiology and Bioinformatics, Université Laval, Québec, Québec, Canada
| | | | - Michel Guertin
- Department
of Biochemistry, Microbiology and Bioinformatics, Université Laval, Québec, Québec, Canada
| | - Guillaume Lamoureux
- Centre for Research
in Molecular Modeling (CERMM), Concordia University, Montréal, Québec, Canada
| | | | - Patrick Lagüe
- Department
of Biochemistry, Microbiology and Bioinformatics, Université Laval, Québec, Québec, Canada
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14
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Sanz-Luque E, Ocaña-Calahorro F, de Montaigu A, Chamizo-Ampudia A, Llamas Á, Galván A, Fernández E. THB1, a truncated hemoglobin, modulates nitric oxide levels and nitrate reductase activity. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 81:467-79. [PMID: 25494936 DOI: 10.1111/tpj.12744] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 11/21/2014] [Accepted: 12/02/2014] [Indexed: 05/18/2023]
Abstract
Hemoglobins are ubiquitous proteins that sense, store and transport oxygen, but the physiological processes in which they are implicated is currently expanding. Recent examples of previously unknown hemoglobin functions, which include scavenging of the signaling molecule nitric oxide (NO), illustrate how the implication of hemoglobins in different cell signaling processes is only starting to be unraveled. The extent and diversity of the hemoglobin protein family suggest that hemoglobins have diverged and have potentially evolved specialized functions in certain organisms. A unique model organism to study this functional diversity at the cellular level is the green alga Chlamydomonas reinhardtii because, among other reasons, it contains an unusually high number of a particular type of hemoglobins known as truncated hemoglobins (THB1-THB12). Here, we reveal a cell signaling function for a truncated hemoglobin of Chlamydomonas that affects the nitrogen assimilation pathway by simultaneously modulating NO levels and nitrate reductase (NR) activity. First, we found that THB1 and THB2 expression is modulated by the nitrogen source and depends on NIT2, a transcription factor required for nitrate assimilation genes expression. Furthermore, THB1 is highly expressed in the presence of NO and is able to convert NO into nitrate in vitro. Finally, THB1 is maintained on its active and reduced form by NR, and in vivo lower expression of THB1 results in increased NR activity. Thus, THB1 plays a dual role in NO detoxification and in the modulation of NR activity. This mechanism can partly explain how NO inhibits NR post-translationally.
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Affiliation(s)
- Emanuel Sanz-Luque
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Córdoba, Campus de Rabanales, Campus de excelencia internacional (CeiA3), Edif. Severo Ochoa, 14071, Córdoba, Spain
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15
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Abstract
The genus Mycobacterium is comprised of Gram-positive bacteria occupying a wide range of natural habitats and includes species that range from severe intracellular pathogens to economically useful and harmless microbes. The recent upsurge in the availability of microbial genome data has shown that genes encoding haemoglobin-like proteins are ubiquitous among Mycobacteria and that multiple haemoglobins (Hbs) of different classes may be present in pathogenic and non-pathogenic species. The occurrence of truncated haemoglobins (trHbs) and flavohaemoglobins (flavoHbs) showing distinct haem active site structures and ligand-binding properties suggests that these Hbs may be playing diverse functions in the cellular metabolism of Mycobacteria. TrHbs and flavoHbs from some of the severe human pathogens such as Mycobacterium tuberculosis and Mycobacterium leprae have been studied recently and their roles in effective detoxification of reactive nitrogen and oxygen species, electron cycling, modulation of redox state of the cell and facilitation of aerobic respiration have been proposed. This multiplicity in the function of Hbs may aid these pathogens to cope with various environmental stresses and survive during their intracellular regime. This chapter provides recent updates on genomic, structural and functional aspects of Mycobacterial Hbs to address their role in Mycobacteria.
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16
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Somasundaram S, Anand RS, Venkatesan P, Paramasivan CN. Bactericidal activity of PA-824 against Mycobacterium tuberculosis under anaerobic conditions and computational analysis of its novel analogues against mutant Ddn receptor. BMC Microbiol 2013; 13:218. [PMID: 24083570 PMCID: PMC3853930 DOI: 10.1186/1471-2180-13-218] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Accepted: 09/27/2013] [Indexed: 11/10/2022] Open
Abstract
Background The resurgence of multi-drug resistant tuberculosis (MDR-TB) and HIV associated tuberculosis (TB) are of serious global concern. To contain this situation, new anti-tuberculosis drugs and reduced treatment regimens are imperative. Recently, a nitroimidazole, PA-824, has been shown to be active against both replicating and non-replicating bacteria. It is activated by the enzyme Deazaflavin-dependent nitroreductase (Ddn) present in Mycobacterium tuberculosis which catalyzes the reduction of PA-824, resulting in the release of lethal reactive nitrogen species (RNS) within the bacteria. In this context, PA-824 was analyzed for its activity against latent tuberculosis under anaerobic conditions and compared with rifampicin (RIF) and pyrazinamide (PZA). Recent mutagenesis studies have identified A76E mutation which affects the above mentioned catalysis and leads to PA-824 resistance. Hence, novel analogues which could cope up with their binding to mutant Ddn receptor were also identified through this study. Results PA-824 at an optimum concentration of 12.5 μg/ml showed enhanced bactericidal activity, resulting in 0 CFU/ml growth when compared to RIF and PZA at normal pH and anaerobic condition. Further docking studies revealed that a combinatorial structure of PA-824 conjugated with moxifloxacin (ligand 8) has the highest binding affinity with the wild type and mutant Ddn receptor. Conclusions PA-824 has been demonstrated to have better activity under anaerobic condition at 12.5 μg/ml, indicating an optimized dose that is required for overcoming the detoxifying mechanisms of M. tuberculosis and inducing its death. Further, the development of resistance through A76E mutation could be overcome through the in silico evolved ligand 8.
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Affiliation(s)
- Sulochana Somasundaram
- Foundation for Innovative New Diagnostics, Flat No, 6-14 (excluding No, 7), 9th floor, Vijaya Building, 17-Barakhamba Road, New Delhi 110 001, India.
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17
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Hospital A, Gelpi JL. High-throughput molecular dynamics simulations: toward a dynamic view of macromolecular structure. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2013. [DOI: 10.1002/wcms.1142] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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18
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Cazade PA, Meuwly M. Oxygen migration pathways in NO-bound truncated hemoglobin. Chemphyschem 2012; 13:4276-86. [PMID: 23161831 DOI: 10.1002/cphc.201200608] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Revised: 09/28/2012] [Indexed: 11/10/2022]
Abstract
Atomistic simulations of dioxygen (O(2)) dynamics and migration in nitric oxide-bound truncated Hemoglobin N (trHbN) of Mycobacterium tuberculosis are reported. From more than 100 ns of simulations the connectivity network involving the metastable states for localization of the O(2) ligand is built and analyzed. It is found that channel I is the primary entrance point for O(2) whereas channel II is predominantly an exit path although access to the protein active site is also possible. For O(2) a new site compared to nitric oxide, from which reaction with the heme group can occur, was found. As this site is close to the heme iron, it could play an important role in the dioxygenation mechanism as O(2) can remain there for hundreds of picoseconds after which it can eventually leave the protein, while NO is localized in Xe2. The present study supports recent experimental work which proposed that O(2) docks in alternative pockets than Xe close to the reactive site. Similar to other proteins, a phenylalanine residue (Phe62) plays the role of a gate along the access route in channel I. The most highly connected site is the Xe3 pocket which is a "hub" and free energy barriers between the different metastable states are ≈1.5 kcal mol(-1) which allows facile O(2) migration within the protein.
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Affiliation(s)
- Pierre-André Cazade
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056, Basel, Switzerland
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19
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Role of PheE15 gate in ligand entry and nitric oxide detoxification function of mycobacterium tuberculosis truncated hemoglobin N. PLoS One 2012; 7:e49291. [PMID: 23145144 PMCID: PMC3493545 DOI: 10.1371/journal.pone.0049291] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2012] [Accepted: 10/08/2012] [Indexed: 11/19/2022] Open
Abstract
The truncated hemoglobin N, HbN, of Mycobacterium tuberculosis is endowed with a potent nitric oxide dioxygenase (NOD) activity that allows it to relieve nitrosative stress and enhance in vivo survival of its host. Despite its small size, the protein matrix of HbN hosts a two-branched tunnel, consisting of orthogonal short and long channels, that connects the heme active site to the protein surface. A novel dual-path mechanism has been suggested to drive migration of O(2) and NO to the distal heme cavity. While oxygen migrates mainly by the short path, a ligand-induced conformational change regulates opening of the long tunnel branch for NO, via a phenylalanine (PheE15) residue that acts as a gate. Site-directed mutagenesis and molecular simulations have been used to examine the gating role played by PheE15 in modulating the NOD function of HbN. Mutants carrying replacement of PheE15 with alanine, isoleucine, tyrosine and tryptophan have similar O(2)/CO association kinetics, but display significant reduction in their NOD function. Molecular simulations substantiated that mutation at the PheE15 gate confers significant changes in the long tunnel, and therefore may affect the migration of ligands. These results support the pivotal role of PheE15 gate in modulating the diffusion of NO via the long tunnel branch in the oxygenated protein, and hence the NOD function of HbN.
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20
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Pond MP, Majumdar A, Lecomte JTJ. Influence of heme post-translational modification and distal ligation on the backbone dynamics of a monomeric hemoglobin. Biochemistry 2012; 51:5733-47. [PMID: 22775272 DOI: 10.1021/bi300624a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The cyanobacterium Synechococcus sp. PCC 7002 uses a hemoglobin of the truncated lineage (GlbN) in the detoxification of reactive species generated in the assimilation of nitrate. In view of a sensing or enzymatic role, several states of GlbN are of interest with respect to its structure-activity relationship. Nuclear magnetic resonance spectroscopy was applied to compare the structure and backbone dynamics of six GlbN forms differing in their oxidation state [Fe(II) or Fe(III)], distal ligand to the iron (histidine, carbon monoxide, or cyanide), or heme post-translational modification (b heme or covalently attached heme). Structural properties were assessed with pseudocontact shift calculations. (15)N relaxation data were analyzed by reduced spectral density mapping (picosecond to nanosecond motions) and by inspection of elevated R(2) values (microsecond to millisecond motions). On the picosecond to nanosecond time scale, GlbN exhibited little flexibility and was unresponsive to the differences among the various forms. Regions of slightly higher mobility were the CE turn, the EF loop, and the H-H' kink. In contrast, fluctuations on the microsecond to millisecond time scale depended on the form. Cyanide binding to the ferric state did not enhance motions, whereas reduction to the ferrous bis-histidine state resulted in elevated R(2) values for several amides. This response was attributed, at least in part, to a weakening of the distal histidine coordination. Carbon monoxide binding quenched some of these fluctuations. The results emphasized the role of the distal ligand in dictating backbone flexibility and illustrated the multiple ways in which motions are controlled by the hemoglobin fold.
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Affiliation(s)
- Matthew P Pond
- T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
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21
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Chapagain PP, Regmi CK, Castillo W. Fluorescent protein barrel fluctuations and oxygen diffusion pathways in mCherry. J Chem Phys 2011; 135:235101. [PMID: 22191901 PMCID: PMC3248888 DOI: 10.1063/1.3660197] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 10/19/2011] [Indexed: 11/14/2022] Open
Abstract
Fluorescent proteins (FPs) are valuable tools as biochemical markers for studying cellular processes. Red fluorescent proteins (RFPs) are highly desirable for in vivo applications because they absorb and emit light in the red region of the spectrum where cellular autofluorescence is low. The naturally occurring fluorescent proteins with emission peaks in this region of the spectrum occur in dimeric or tetrameric forms. The development of mutant monomeric variants of RFPs has resulted in several novel FPs known as mFruits. Though oxygen is required for maturation of the chromophore, it is known that photobleaching of FPs is oxygen sensitive, and oxygen-free conditions result in improved photostabilities. Therefore, understanding oxygen diffusion pathways in FPs is important for both photostabilites and maturation of the chromophores. In this paper, we use molecular dynamics calculations to investigate the protein barrel fluctuations in mCherry, which is one of the most useful monomeric mFruit variant. We employ implicit ligand sampling to determine oxygen pathways from the bulk solvent into the mCherry chromophore in the interior of the protein. We also show that these pathways can be blocked or altered and barrel fluctuations can be reduced by strategic amino acid substitutions.
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Affiliation(s)
- Prem P Chapagain
- Department of Physics, Florida International University, Miami, Florida 33199, USA.
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22
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Savard PY, Daigle R, Morin S, Sebilo A, Meindre F, Lagüe P, Guertin M, Gagné SM. Structure and dynamics of Mycobacterium tuberculosis truncated hemoglobin N: insights from NMR spectroscopy and molecular dynamics simulations. Biochemistry 2011; 50:11121-30. [PMID: 21999759 DOI: 10.1021/bi201059a] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The potent nitric oxide dioxygenase (NOD) activity (trHbN-Fe²⁺-O₂ + (•)NO → trHbN-Fe³⁺-OH₂ + NO₃⁻) of Mycobacterium tuberculosis truncated hemoglobin N (trHbN) protects aerobic respiration from inhibition by (•)NO. The high activity of trHbN has been attributed in part to the presence of numerous short-lived hydrophobic cavities that allow partition and diffusion of the gaseous substrates (•)NO and O₂ to the active site. We investigated the relation between these cavities and the dynamics of the protein using solution NMR spectroscopy and molecular dynamics (MD). Results from both approaches indicate that the protein is mainly rigid with very limited motions of the backbone N-H bond vectors on the picoseconds-nanoseconds time scale, indicating that substrate diffusion and partition within trHbN may be controlled by side-chains movements. Model-free analysis also revealed the presence of slow motions (microseconds-milliseconds), not observed in MD simulations, for many residues located in helices B and G including the distal heme pocket Tyr33(B10). All currently known crystal structures and molecular dynamics data of truncated hemoglobins with the so-called pre-A N-terminal extension suggest a stable α-helical conformation that extends in solution. Moreover, a recent study attributed a crucial role to the pre-A helix for NOD activity. However, solution NMR data clearly show that in near-physiological conditions these residues do not adopt an α-helical conformation and are significantly disordered and that the helical conformation seen in crystal structures is likely induced by crystal contacts. Although this lack of order for the pre-A does not disagree with an important functional role for these residues, our data show that one should not assume an helical conformation for these residues in any functional interpretation. Moreover, future molecular dynamics simulations should not use an initial α-helical conformation for these residues in order to avoid a bias based on an erroneous initial structure for the N-termini residues. This work constitutes the first study of a truncated hemoglobin dynamics performed by solution heteronuclear relaxation NMR spectroscopy.
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Affiliation(s)
- Pierre-Yves Savard
- Département de biochimie, de microbiologie et de bio-informatique, Université Laval and PROTEO, Québec, Canada
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23
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Heroux MS, Mohan AD, Olsen KW. Ligand migration in the truncated hemoglobin of Mycobacterium tuberculosis. IUBMB Life 2011; 63:214-20. [DOI: 10.1002/iub.438] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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24
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Scott NL, Xu Y, Shen G, Vuletich DA, Falzone CJ, Li Z, Ludwig M, Pond MP, Preimesberger MR, Bryant DA, Lecomte JTJ. Functional and Structural Characterization of the 2/2 Hemoglobin from Synechococcus sp. PCC 7002,. Biochemistry 2010; 49:7000-11. [DOI: 10.1021/bi100463d] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Yu Xu
- Department of Biochemistry and Molecular Biology
| | | | | | | | - Zhongkui Li
- Department of Biochemistry and Molecular Biology
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25
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Theoretical investigations of nitric oxide channeling in Mycobacterium tuberculosis truncated hemoglobin N. Biophys J 2010; 97:2967-77. [PMID: 19948126 DOI: 10.1016/j.bpj.2009.09.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 08/28/2009] [Accepted: 09/02/2009] [Indexed: 11/22/2022] Open
Abstract
Mycobacterium tuberculosis group I truncated hemoglobin trHbN catalyzes the oxidation of nitric oxide (NO) to nitrate with a second-order rate constant k approximately 745 microM(-1) s(-1) at 23 degrees C (nitric oxide dioxygenase reaction). It was proposed that this high efficiency is associated with the presence of hydrophobic tunnels inside trHbN structure that allow substrate diffusion to the distal heme pocket. In this work, we investigated the mechanisms of NO diffusion within trHbN tunnels in the context of the nitric oxide dioxygenase reaction using two independent approaches. Molecular dynamics simulations of trHbN were performed in the presence of explicit NO molecules. Successful NO diffusion from the bulk solvent to the distal heme pocket was observed in all simulations performed. The simulations revealed that NO interacts with trHbN at specific surface sites, composed of hydrophobic residues located at tunnel entrances. The entry and the internal diffusion of NO inside trHbN were performed using the Long, Short, and EH tunnels reported earlier. The Short tunnel was preferentially used by NO to reach the distal heme pocket. This preference is ascribed to its hydrophobic funnel-shape entrance, covering a large area extending far from the tunnel entrance. This funnel-shape entrance triggers the frequent formation of solvent-excluded cavities capable of hosting up to three NO molecules, thereby accelerating NO capture and entry. The importance of hydrophobicity of entrances for NO capture is highlighted by a comparison with a polar mutant for which residues at entrances were mutated with polar residues. A complete map of NO diffusion pathways inside trHbN matrix was calculated, and NO molecules were found to diffuse from Xe cavity to Xe cavity. This scheme was in perfect agreement with the three-dimensional free-energy distribution calculated using implicit ligand sampling. The trajectories showed that NO significantly alters the dynamics of the key amino acids of Phe(62)(E15), a residue proposed to act as a gate controlling ligand traffic inside the Long tunnel, and also of Ile(119)(H11), at the entrance of the Short tunnel. It is noteworthy that NO diffusion inside trHbN tunnels is much faster than that reported previously for myoglobin. The results presented in this work shed light on the diffusion mechanism of apolar gaseous substrates inside protein matrix.
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26
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Baron R, McCammon JA, Mattevi A. The oxygen-binding vs. oxygen-consuming paradigm in biocatalysis: structural biology and biomolecular simulation. Curr Opin Struct Biol 2009; 19:672-9. [DOI: 10.1016/j.sbi.2009.10.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Accepted: 10/07/2009] [Indexed: 11/28/2022]
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Finding molecular dioxygen tunnels in homoprotocatechuate 2,3-dioxygenase: implications for different reactivity of identical subunits. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:327-36. [PMID: 19826803 DOI: 10.1007/s00249-009-0551-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Revised: 09/09/2009] [Accepted: 09/24/2009] [Indexed: 10/20/2022]
Abstract
Extradiol dioxygenases facilitate microbial aerobic degradation of catechol and its derivatives by activating molecular dioxygen and incorporating both oxygen atoms into their substrates. Experimental and theoretical studies have focused on the mechanism of the reaction at the active site. However, whether the catalytic rate is limited by O(2) access to the active site has not yet been explored. Here, we choose a recently solved X-ray structure of homoprotocatechuate 2,3-dioxygenase as a typical example to determine potential pathways for O(2) migration from the solvent into the enzyme center. On the basis of the trajectories of two 10-ns molecular dynamics simulations, implicit ligand sampling was used to calculate the 3D free energy map for O(2) inside the protein. The energetically optimal routes for O(2) diffusion were identified for each subunit of the homotetrameric protein structure. The O(2) tunnels formed because of thermal fluctuations were also characterized by connecting elongated cavities inside the protein. By superimposing the favorable O(2) tunnels on to the free energy map, both energetically and geometrically preferred O(2) pathways were determined, as also were the amino acids that may be critical for O(2) passage along these paths. Our results demonstrate that identical subunits possess quite distinct O(2) tunnels. The order of O(2) affinity of these tunnels is generally consistent with the order of the catalytic rate of each subunit. As a consequence, the probability of finding the reaction product is highest in the subunit containing the highest O(2) affinity pathway.
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28
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Xu L, Liu X, Zhao W, Wang X. Locally Enhanced Sampling Study of Dioxygen Diffusion Pathways in Homoprotocatechuate 2,3-Dioxygenase. J Phys Chem B 2009; 113:13596-603. [DOI: 10.1021/jp902597t] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Liang Xu
- Department of Engineering Mechanics, State Key Laboratory of Structural Analyses for Industrial Equipment, and Department of Chemistry, Dalian University of Technology, Dalian 116023, China, and School of Chemical Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
| | - Xin Liu
- Department of Engineering Mechanics, State Key Laboratory of Structural Analyses for Industrial Equipment, and Department of Chemistry, Dalian University of Technology, Dalian 116023, China, and School of Chemical Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
| | - Weijie Zhao
- Department of Engineering Mechanics, State Key Laboratory of Structural Analyses for Industrial Equipment, and Department of Chemistry, Dalian University of Technology, Dalian 116023, China, and School of Chemical Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
| | - Xicheng Wang
- Department of Engineering Mechanics, State Key Laboratory of Structural Analyses for Industrial Equipment, and Department of Chemistry, Dalian University of Technology, Dalian 116023, China, and School of Chemical Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
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