1
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Gindt YM, Connolly G, Vonder Haar AL, Kikhwa M, Schelvis JPM. Investigation of the pH-dependence of the oxidation of FAD in VcCRY-1, a member of the cryptochrome-DASH family. Photochem Photobiol Sci 2021; 20:831-841. [PMID: 34091863 DOI: 10.1007/s43630-021-00063-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 05/31/2021] [Indexed: 11/29/2022]
Abstract
Vibrio cholerae cryptochrome-1 (VcCRY-1) is a member of the cryptochrome DASH family. The flavoprotein appears to use blue light both for repair of cyclobutane pyrimidine dimers (CPDs) on DNA and signal transduction. Earlier, we found that it was almost impossible to oxidize the FADH· state upon binding to a CPD, and, in the absence of substrate, the rate of FADH· oxidation was much larger at high pH (Gindt et al. in Biochemistry 54:2802-2805, 2015). Here, we present the pH-dependence of the oxidation of FADH· by ferricyanide, which revealed a switch between slow and fast oxidation with a pKa ≈ 7.0. Stopped-flow mixing was used to measure the oxidation of FADH- to FADH· at pH 6.7 and 7.5. Substrate binding was required to slow down this oxidation such that it could be measured with stopped flow, but there was only a small effect of pH. In addition, resonance Raman measurements of FADH· in VcCRY-1 at pH 6.5 and 7.5 were performed to probe for structural changes near the FAD cofactor related to the observed changes in rate of FADH· oxidation. Only substrate binding seemed to induce a change near the FAD cofactor that may relate to the change in oxidation kinetics. The pH-effect on the FADH· oxidation rate, which is rate-limited by the proton acceptor, does not seem to be due to a protein structural change near the FAD cofactor. Instead, a conserved glutamate in CRY-DASH may control the deprotonation of FADH· and give rise to the pH-effect.
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Affiliation(s)
- Yvonne M Gindt
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, NJ, 07043, USA
| | - Gabrielle Connolly
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, NJ, 07043, USA
| | - Amy L Vonder Haar
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, NJ, 07043, USA
| | - Miryam Kikhwa
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, NJ, 07043, USA
| | - Johannes P M Schelvis
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, NJ, 07043, USA.
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2
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Hernández-Rodríguez EW, Escorcia AM, van der Kamp MW, Montero-Alejo AL, Caballero J. Multi-scale simulation reveals that an amino acid substitution increases photosensitizing reaction inputs in Rhodopsins. J Comput Chem 2020; 41:2278-2295. [PMID: 32757375 DOI: 10.1002/jcc.26392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Revised: 06/27/2020] [Accepted: 07/04/2020] [Indexed: 11/11/2022]
Abstract
Evaluating the availability of molecular oxygen (O2 ) and energy of excited states in the retinal binding site of rhodopsin is a crucial challenging first step to understand photosensitizing reactions in wild-type (WT) and mutant rhodopsins by absorbing visible light. In the present work, energies of the ground and excited states related to 11-cis-retinal and the O2 accessibility to the β-ionone ring are evaluated inside WT and human M207R mutant rhodopsins. Putative O2 pathways within rhodopsins are identified by using molecular dynamics simulations, Voronoi-diagram analysis, and implicit ligand sampling while retinal energetic properties are investigated through density functional theory, and quantum mechanical/molecular mechanical methods. Here, the predictions reveal that an amino acid substitution can lead to enough energy and O2 accessibility in the core hosting retinal of mutant rhodopsins to favor the photosensitized singlet oxygen generation, which can be useful in understanding retinal degeneration mechanisms and in designing blue-lighting-absorbing proteic photosensitizers.
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Affiliation(s)
- Erix W Hernández-Rodríguez
- Laboratorio de Bioinformática y Química Computacional, Escuela de Química y Farmacia, Facultad de Medicina, Universidad Católica del Maule, Talca, Chile
| | - Andrés M Escorcia
- School of Biochemistry, University of Bristol, University Walk, Bristol, UK
| | | | - Ana L Montero-Alejo
- Departamento de Física, Facultad de Ciencias Naturales, Matemática y del Medio Ambiente (FCNMM), Universidad Tecnológica Metropolitana, Santiago, Chile
| | - Julio Caballero
- Departamento de Bioinformática, Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería, Universidad de Talca, Talca, Chile
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3
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Domene C, Jorgensen C, Schofield CJ. Mechanism of Molecular Oxygen Diffusion in a Hypoxia-Sensing Prolyl Hydroxylase Using Multiscale Simulation. J Am Chem Soc 2020; 142:2253-2263. [DOI: 10.1021/jacs.9b09236] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Carmen Domene
- Chemistry Research Laboratory, Mansfield Road, University of Oxford, Oxford OX1 3TA, United Kingdom
- Department of Chemistry, Britannia House, King’s College London, 7 Trinity Street, London SE1 1DB, United Kingdom
- Department of Chemistry, University of Bath, Claverton Down Bath BA2 7AY, United Kingdom
| | - Christian Jorgensen
- Department of Chemistry, Britannia House, King’s College London, 7 Trinity Street, London SE1 1DB, United Kingdom
| | - Christopher J. Schofield
- Chemistry Research Laboratory, Mansfield Road, University of Oxford, Oxford OX1 3TA, United Kingdom
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4
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Yang Y, Liu F, Liu A. Adapting to oxygen: 3-Hydroxyanthrinilate 3,4-dioxygenase employs loop dynamics to accommodate two substrates with disparate polarities. J Biol Chem 2018; 293:10415-10424. [PMID: 29784877 DOI: 10.1074/jbc.ra118.002698] [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: 03/01/2018] [Revised: 05/18/2018] [Indexed: 11/06/2022] Open
Abstract
3-Hydroxyanthranilate 3,4-dioxygenase (HAO) is an iron-dependent protein that activates O2 and inserts both oxygen atoms into 3-hydroxyanthranilate (3-HAA). An intriguing question is how HAO can rapidly bind O2, even though local O2 concentrations and diffusion rates are relatively low. Here, a close inspection of the HAO structures revealed that substrate- and inhibitor-bound structures exhibit a closed conformation with three hydrophobic loop regions moving toward the catalytic iron center, whereas the ligand-free structure is open. We hypothesized that these loop movements enhance O2 binding to the binary complex of HAO and 3-HAA. We found that the carboxyl end of 3-HAA triggers changes in two loop regions and that the third loop movement appears to be driven by an H-bond interaction between Asn27 and Ile142 Mutational analyses revealed that N27A, I142A, and I142P variants cannot form a closed conformation, and steady-state kinetic assays indicated that these variants have a substantially higher Km for O2 than WT HAO. This observation suggested enhanced hydrophobicity at the iron center resulting from the concerted loop movements after the binding of the primary substrate, which is hydrophilic. Given that O2 is nonpolar, the increased hydrophobicity at the iron center of the binary complex appears to be essential for rapid O2 binding and activation, explaining the reason for the 3-HAA-induced loop movements. Because substrate binding-induced open-to-closed conformational changes are common, the results reported here may help further our understanding of how oxygen is enriched in nonheme iron-dependent dioxygenases.
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Affiliation(s)
- Yu Yang
- From the Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249 and
| | - Fange Liu
- the Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Aimin Liu
- From the Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249 and
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5
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Enzymatic control of dioxygen binding and functionalization of the flavin cofactor. Proc Natl Acad Sci U S A 2018; 115:4909-4914. [PMID: 29686059 DOI: 10.1073/pnas.1801189115] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The reactions of enzymes and cofactors with gaseous molecules such as dioxygen (O2) are challenging to study and remain among the most contentious subjects in biochemistry. To date, it is largely enigmatic how enzymes control and fine-tune their reactions with O2, as exemplified by the ubiquitous flavin-dependent enzymes that commonly facilitate redox chemistry such as the oxygenation of organic substrates. Here we employ O2-pressurized X-ray crystallography and quantum mechanical calculations to reveal how the precise positioning of O2 within a flavoenzyme's active site enables the regiospecific formation of a covalent flavin-oxygen adduct and oxygenating species (i.e., the flavin-N5-oxide) by mimicking a critical transition state. This study unambiguously demonstrates how enzymes may control the O2 functionalization of an organic cofactor as prerequisite for oxidative catalysis. Our work thus illustrates how O2 reactivity can be harnessed in an enzymatic environment and provides crucial knowledge for future rational design of O2-reactive enzymes.
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6
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Dynamics of dehaloperoxidase-hemoglobin A derived from NMR relaxation spectroscopy and molecular dynamics simulation. J Inorg Biochem 2018; 181:65-73. [DOI: 10.1016/j.jinorgbio.2018.01.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 12/11/2017] [Accepted: 01/07/2018] [Indexed: 11/18/2022]
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7
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Westberg M, Bregnhøj M, Etzerodt M, Ogilby PR. No Photon Wasted: An Efficient and Selective Singlet Oxygen Photosensitizing Protein. J Phys Chem B 2017; 121:9366-9371. [PMID: 28892628 DOI: 10.1021/acs.jpcb.7b07831] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Optogenetics has been, and will continue to be, a boon to mechanistic studies of cellular processes. Genetically encodable proteins that sensitize the production of reactive oxygen species (ROS) are expected to play an increasingly important role, particularly in elucidating mechanisms of temporally and spatially dependent cell signaling. However, a substantial challenge in developing such photosensitizing proteins has been to funnel the optical excitation energy into the initial selective production of only one ROS. Singlet molecular oxygen, O2(a1Δg), is a ROS known to have a wide range of effects on cell function. Nevertheless, mechanistic details of singlet oxygen's behavior in a cell are lacking. On the basis of the rational optimization of a LOV-derived flavoprotein, we now report the development and photophysical characterization of a protein-encased photosensitizer that efficiently and selectively produces singlet oxygen at the expense of other ROS, especially ROS that derive from photoinduced electron transfer reactions. These results set the stage for a plethora of new experiments to elucidate ROS-mediated events in cells.
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Affiliation(s)
- Michael Westberg
- Department of Chemistry, Aarhus University , DK-8000 Aarhus, Denmark
| | - Mikkel Bregnhøj
- Department of Chemistry, Aarhus University , DK-8000 Aarhus, Denmark
| | - Michael Etzerodt
- Department of Molecular Biology and Genetics, Aarhus University , DK-8000 Aarhus, Denmark
| | - Peter R Ogilby
- Department of Chemistry, Aarhus University , DK-8000 Aarhus, Denmark
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8
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Westberg M, Bregnhøj M, Etzerodt M, Ogilby PR. Temperature Sensitive Singlet Oxygen Photosensitization by LOV-Derived Fluorescent Flavoproteins. J Phys Chem B 2017; 121:2561-2574. [PMID: 28257211 DOI: 10.1021/acs.jpcb.7b00561] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Optogenetic sensitizers that selectively produce a given reactive oxygen species (ROS) constitute a promising tool for studying cell signaling processes with high levels of spatiotemporal control. However, to harness the full potential of this tool for live cell studies, the photophysics of currently available systems need to be explored further and optimized. Of particular interest in this regard, are the flavoproteins miniSOG and SOPP, both of which (1) contain the chromophore flavin mononucleotide, FMN, in a LOV-derived protein enclosure, and (2) photosensitize the production of singlet oxygen, O2(a1Δg). Here we present an extensive experimental study of the singlet and triplet state photophysics of FMN in SOPP and miniSOG over a physiologically relevant temperature range. Although changes in temperature only affect the singlet excited state photophysics slightly, the processes that influence the deactivation of the triplet excited state are more sensitive to temperature. Most notably, for both proteins, the rate constant for quenching of 3FMN by ground state oxygen, O2(X3Σg-), increases ∼10-fold upon increasing the temperature from 10 to 43 °C, while the oxygen-independent channels of triplet state deactivation are less affected. As a consequence, this increase in temperature results in higher yields of O2(a1Δg) formation for both SOPP and miniSOG. We also show that the quantum yields of O2(a1Δg) production by both miniSOG and SOPP are mainly limited by the fraction of FMN triplet states quenched by O2(X3Σg-). The results presented herein provide a much-needed quantitative framework that will facilitate the future development of optogenetic ROS sensitizers.
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Affiliation(s)
- Michael Westberg
- Department of Chemistry, Aarhus University , DK-8000 Aarhus, Denmark
| | - Mikkel Bregnhøj
- Department of Chemistry, Aarhus University , DK-8000 Aarhus, Denmark
| | - Michael Etzerodt
- Department of Molecular Biology and Genetics, Aarhus University , DK-8000 Aarhus, Denmark
| | - Peter R Ogilby
- Department of Chemistry, Aarhus University , DK-8000 Aarhus, Denmark
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9
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Javanainen M, Vattulainen I, Monticelli L. On Atomistic Models for Molecular Oxygen. J Phys Chem B 2017; 121:518-528. [PMID: 28004930 DOI: 10.1021/acs.jpcb.6b11183] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Molecular oxygen (O2) is key to all life on earth, as it is constantly cycled via photosynthesis and cellular respiration. Substantial scientific effort has been devoted to understanding every part of this cycle. Classical molecular dynamics (MD) simulations have been used to study some of the key processes involved in cellular respiration: O2 permeation through alveolar monolayers and cellular membranes, its binding to hemoglobin during transport in the bloodstream, as well as its transport along optimal pathways toward its reduction sites in proteins. Moreover, MD simulations can help interpret the results of several imaging techniques in which O2 is used because of its paramagnetic nature. However, despite the widespread use of computational models for the O2 molecule, their performances have never been systematically evaluated. In this paper, we assess the performances of 14 different models of O2 available in the literature by calculating four thermodynamic properties: density, heat of vaporization, free energy of hydration, and free energy of solvation in hexadecane. For each property, reliable experimental data are available. Most models perform reasonably well in predicting the correct trends, but they fail to reproduce the experimental data quantitatively. We then develop new models for O2, with and without a quadrupole moment, and compare their behavior with the behavior of previously published models. The new models show significant improvement in terms of density, heat of vaporization, and free energy of hydration. However, quantitative agreement with water-oil partitioning is not reached due to discrepancies between the calculated and measured free energies of solvation in hexadecane. We suggest that classical pairwise-additive models may be inadequate to properly describe the thermodynamics of solvation of apolar species, such as O2, in apolar solvents.
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Affiliation(s)
- Matti Javanainen
- Department of Physics, Tampere University of Technology , 33720 Tampere, Finland.,Department of Physics, University of Helsinki , 00100 Helsinki, Finland
| | - Ilpo Vattulainen
- Department of Physics, Tampere University of Technology , 33720 Tampere, Finland.,Department of Physics, University of Helsinki , 00100 Helsinki, Finland.,MEMPHYS - Centre for Biomembrane Physics, University of Southern Denmark , 5230 Odense, Denmark
| | - Luca Monticelli
- University of Lyon, CNRS, UMR 5086 MMSB , 69367 Lyon, France
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10
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Ebert MCCJC, Dürr SL, A. Houle A, Lamoureux G, Pelletier JN. Evolution of P450 Monooxygenases toward Formation of Transient Channels and Exclusion of Nonproductive Gases. ACS Catal 2016. [DOI: 10.1021/acscatal.6b02154] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Maximilian C. C. J. C. Ebert
- Département
de biochimie, Université de Montréal, Montréal H3T 1J4, Canada
- PROTEO, The Québec Network for Research on Protein Function, Engineering and Applications, Québec G1V 0A6, Canada
- CGCC, the Center for Green Chemistry and Catalysis, Montréal H3T 1J4, Canada
| | - Simon L. Dürr
- PROTEO, The Québec Network for Research on Protein Function, Engineering and Applications, Québec G1V 0A6, Canada
- CGCC, the Center for Green Chemistry and Catalysis, Montréal H3T 1J4, Canada
- Département
de chimie, Université de Montréal, Montréal H3T 1J4, Canada
| | - Armande A. Houle
- Département
de biochimie, Université de Montréal, Montréal H3T 1J4, Canada
- PROTEO, The Québec Network for Research on Protein Function, Engineering and Applications, Québec G1V 0A6, Canada
- CGCC, the Center for Green Chemistry and Catalysis, Montréal H3T 1J4, Canada
| | - Guillaume Lamoureux
- PROTEO, The Québec Network for Research on Protein Function, Engineering and Applications, Québec G1V 0A6, Canada
- Department
of Chemistry and Biochemistry and Centre for Research in Molecular
Modeling (CERMM), Concordia University, Montreal H4B 1R6, Canada
| | - Joelle N. Pelletier
- Département
de biochimie, Université de Montréal, Montréal H3T 1J4, Canada
- PROTEO, The Québec Network for Research on Protein Function, Engineering and Applications, Québec G1V 0A6, Canada
- CGCC, the Center for Green Chemistry and Catalysis, Montréal H3T 1J4, Canada
- Département
de chimie, Université de Montréal, Montréal H3T 1J4, Canada
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11
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Shadrina MS, English AM, Peslherbe GH. Benchmarking Rapid TLES Simulations of Gas Diffusion in Proteins: Mapping O2 Migration and Escape in Myoglobin as a Case Study. J Chem Theory Comput 2016; 12:2038-46. [PMID: 26938707 DOI: 10.1021/acs.jctc.5b01132] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Standard molecular dynamics (MD) simulations of gas diffusion consume considerable computational time and resources even for small proteins. To combat this, temperature-controlled locally enhanced sampling (TLES) examines multiple diffusion trajectories per simulation by accommodating multiple noninteracting copies of a gas molecule that diffuse independently, while the protein and water molecules experience an average interaction from all copies. Furthermore, gas migration within a protein matrix can be accelerated without altering protein dynamics by increasing the effective temperature of the TLES copies. These features of TLES enable rapid simulations of gas diffusion within a protein matrix at significantly reduced (∼98%) computational cost. However, the results of TLES and standard MD simulations have not been systematically compared, which limits the adoption of the TLES approach. We address this drawback here by benchmarking TLES against standard MD in the simulation of O2 diffusion in myoglobin (Mb) as a case study since this model system has been extensively characterized. We find that 2 ns TLES and 108 ns standard simulations map the same network of diffusion tunnels in Mb and uncover the same docking sites, barriers, and escape portals. We further discuss the influence of simulation time as well as the number of independent simulations on the O2 population density within the diffusion tunnels and on the sampling of Mb's conformational space as revealed by principal component analysis. Overall, our comprehensive benchmarking reveals that TLES is an appropriate and robust tool for the rapid mapping of gas diffusion in proteins when the kinetic data provided by standard MD are not required. Furthermore, TLES provides explicit ligand diffusion pathways, unlike most rapid methods.
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Affiliation(s)
- Maria S Shadrina
- Centre for Research in Molecular Modeling (CERMM) and Department of Chemistry and Biochemistry, Concordia University , 7141 Sherbrooke Street West, Montréal, Québec, Canada H4B 1R6
| | - Ann M English
- Centre for Research in Molecular Modeling (CERMM) and Department of Chemistry and Biochemistry, Concordia University , 7141 Sherbrooke Street West, Montréal, Québec, Canada H4B 1R6
| | - Gilles H Peslherbe
- Centre for Research in Molecular Modeling (CERMM) and Department of Chemistry and Biochemistry, Concordia University , 7141 Sherbrooke Street West, Montréal, Québec, Canada H4B 1R6
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12
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Mahinthichaichan P, Gennis RB, Tajkhorshid E. All the O2 Consumed by Thermus thermophilus Cytochrome ba3 Is Delivered to the Active Site through a Long, Open Hydrophobic Tunnel with Entrances within the Lipid Bilayer. Biochemistry 2016; 55:1265-78. [PMID: 26845082 DOI: 10.1021/acs.biochem.5b01255] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Cytochrome ba3 is a proton-pumping heme-copper oxygen reductase from the extreme thermophile Thermus thermophilus. Despite the fact that the enzyme's active site is buried deep within the protein, the apparent second order rate constant for the initial binding of O2 to the active-site heme has been experimentally found to be 10(9) M(-1) s(-1) at 298 K, at or near the diffusion limit, and 2 orders of magnitude faster than for O2 binding to myoglobin. To provide quantitative and microscopic descriptions of the O2 delivery pathway and mechanism in cytochrome ba3, extensive molecular dynamics simulations of the enzyme in its membrane-embedded form have been performed, including different protocols of explicit ligand sampling (flooding) simulations with O2, implicit ligand sampling analysis, and in silico mutagenesis. The results show that O2 diffuses to the active site exclusively via a Y-shaped hydrophobic tunnel with two 25-Å long membrane-accessible branches that coincide with the pathway previously suggested by the crystallographically identified xenon binding sites. The two entrances of the bifurcated tunnel of cytochrome ba3 are located within the lipid bilayer, where O2 is preferentially partitioned from the aqueous phase. The largest barrier to O2 migration within the tunnel is estimated to be only 1.5 kcal/mol, allowing O2 to reach the enzyme active site virtually impeded by one-dimensional diffusion once it reaches a tunnel entrance at the protein surface. Unlike other O2-utilizing proteins, the tunnel is "open" with no transient barriers observed due to protein dynamics. This unique low-barrier passage through the protein ensures that O2 transit through the protein is never rate-limiting.
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Affiliation(s)
- Paween Mahinthichaichan
- Department of Biochemistry, and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Robert B Gennis
- Department of Biochemistry, and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Emad Tajkhorshid
- Department of Biochemistry, and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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13
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Abstract
Internal cavities are important elements in protein structure, dynamics, stability and function. Here we use NMR spectroscopy to investigate the binding of molecular oxygen (O2) to cavities in a well-studied model for ligand binding, the L99A mutant of T4 lysozyme. On increasing the O2 concentration to 8.9 mM, changes in 1H, 15N, and 13C chemical shifts and signal broadening were observed specifically for backbone amide and side chain methyl groups located around the two hydrophobic cavities of the protein. O2-induced longitudinal relaxation enhancements for amide and methyl protons could be adequately accounted for by paramagnetic dipolar relaxation. These data provide the first experimental demonstration that O2 binds specifically to the hydrophobic, and not the hydrophilic cavities, in a protein. Molecular dynamics simulations visualized the rotational and translational motions of O2 in the cavities, as well as the binding and egress of O2, suggesting that the channel consisting of helices D, E, G, H, and J could be the potential gateway for ligand binding to the protein. Due to strong paramagnetic relaxation effects, O2 gas-pressure NMR measurements can detect hydrophobic cavities when populated to as little as 1%, and thereby provide a general and highly sensitive method for detecting oxygen binding in proteins.
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14
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Computation of Rate Constants for Diffusion of Small Ligands to and from Buried Protein Active Sites. Methods Enzymol 2016; 578:299-326. [DOI: 10.1016/bs.mie.2016.05.039] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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15
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Shadrina MS, Peslherbe GH, English AM. Quaternary-Linked Changes in Structure and Dynamics That Modulate O2 Migration within Hemoglobin’s Gas Diffusion Tunnels. Biochemistry 2015; 54:5268-78. [DOI: 10.1021/acs.biochem.5b00368] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Maria S. Shadrina
- Department of Chemistry and
Biochemistry, Centre for Research in Molecular Modeling and PROTEO, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Gilles H. Peslherbe
- Department of Chemistry and
Biochemistry, Centre for Research in Molecular Modeling and PROTEO, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Ann M. English
- Department of Chemistry and
Biochemistry, Centre for Research in Molecular Modeling and PROTEO, Concordia University, Montreal, Quebec H4B 1R6, Canada
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16
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Shadrina MS, Peslherbe GH, English AM. O2 and Water Migration Pathways between the Solvent and Heme Pockets of Hemoglobin with Open and Closed Conformations of the Distal HisE7. Biochemistry 2015; 54:5279-89. [PMID: 26226401 DOI: 10.1021/acs.biochem.5b00369] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hemoglobin transports O2 by binding the gas at its four hemes. Hydrogen bonding between the distal histidine (HisE7) and heme-bound O2 significantly increases the affinity of human hemoglobin (HbA) for this ligand. HisE7 is also proposed to regulate the release of O2 to the solvent via a transient E7 channel. To reveal the O2 escape routes controlled by HisE7 and to evaluate its role in gating heme access, we compare simulations of O2 diffusion from the distal heme pockets of the T and R states of HbA performed with HisE7 in its open (protonated) and closed (neutral) conformations. Irrespective of HisE7's conformation, we observe the same four or five escape routes leading directly from the α- or β-distal heme pockets to the solvent. Only 21-53% of O2 escapes occur via these routes, with the remainder escaping through routes that encompass multiple internal cavities in HbA. The conformation of the distal HisE7 controls the escape of O2 from the heme by altering the distal pocket architecture in a pH-dependent manner, not by gating the E7 channel. Removal of the HisE7 side chain in the GlyE7 variant exposes the distal pockets to the solvent, and the percentage of O2 escapes to the solvent directly from the α- or β-distal pockets of the mutant increases to 70-88%. In contrast to O2, the dominant water route from the bulk solvent is gated by HisE7 because protonation and opening of this residue dramatically increase the rate of influx of water into the empty distal heme pockets. The occupancy of the distal heme site by a water molecule, which functions as an additional nonprotein barrier to binding of the ligand to the heme, is also controlled by HisE7. Overall, analysis of gas and water diffusion routes in the subunits of HbA and its GlyE7 variant sheds light on the contribution of distal HisE7 in controlling polar and nonpolar ligand movement between the solvent and the hemes.
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Affiliation(s)
- Maria S Shadrina
- Department of Chemistry and Biochemistry, Centre for Research in Molecular Modeling and PROTEO, Concordia University , Montreal, Quebec H4B 1R6, Canada
| | - Gilles H Peslherbe
- Department of Chemistry and Biochemistry, Centre for Research in Molecular Modeling and PROTEO, Concordia University , Montreal, Quebec H4B 1R6, Canada
| | - Ann M English
- Department of Chemistry and Biochemistry, Centre for Research in Molecular Modeling and PROTEO, Concordia University , Montreal, Quebec H4B 1R6, Canada
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17
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Di Russo NV, Condurso HL, Li K, Bruner SD, Roitberg AE. Oxygen diffusion pathways in a cofactor-independent dioxygenase. Chem Sci 2015; 6:6341-6348. [PMID: 26508997 PMCID: PMC4618494 DOI: 10.1039/c5sc01638j] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A combination of experimental and computational studies reveals the main O2 diffusion pathways, providing insight into how cofactor-independent oxygenases control stereospecificity and prevent oxidative inactivation.
Molecular oxygen plays an important role in a wide variety of enzymatic reactions. Through recent research efforts combining computational and experimental methods a new view of O2 diffusion is emerging, where specific channels guide O2 to the active site. The focus of this work is DpgC, a cofactor-independent oxygenase. Molecular dynamics simulations, together with mutagenesis experiments and xenon-binding data, reveal that O2 reaches the active site of this enzyme using three main pathways and four different access points. These pathways connect a series of dynamic hydrophobic pockets, concentrating O2 at a specific face of the enzyme substrate. Extensive molecular dynamics simulations provide information about which pathways are more frequently used. This data is consistent with the results of kinetic measurements on mutants and is difficult to obtain using computational cavity-location methods. Taken together, our results reveal that although DpgC is rare in its ability of activating O2 in the absence of cofactors or metals, the way O2 reaches the active site is similar to that reported for other O2-using proteins: multiple access channels are available, and the architecture of the pathway network can provide regio- and stereoselectivity. Our results point to the existence of common themes in O2 access that are conserved among very different types of proteins.
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Affiliation(s)
- Natali V Di Russo
- Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA
| | - Heather L Condurso
- Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA
| | - Kunhua Li
- Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA
| | - Steven D Bruner
- Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA
| | - Adrian E Roitberg
- Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA
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18
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De Sancho D, Kubas A, Wang PH, Blumberger J, Best RB. Identification of Mutational Hot Spots for Substrate Diffusion: Application to Myoglobin. J Chem Theory Comput 2015; 11:1919-27. [PMID: 26574395 PMCID: PMC6132223 DOI: 10.1021/ct5011455] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The pathways by which small molecules (substrates or inhibitors) access active sites are a key aspect of the function of enzymes and other proteins. A key problem in designing or altering such proteins is to identify sites for mutation that will have the desired effect on the substrate transport properties. While specific access channels have been invoked in the past, molecular simulations suggest that multiple routes are possible, complicating the analysis. This complexity, however, can be captured by a Markov State Model (MSM) of the ligand diffusion process. We have developed a sensitivity analysis of the resulting rate matrix, which identifies the locations where mutations should have the largest effect on the diffusive on rate. We apply this method to myoglobin, which is the best characterized example both from experiment and simulation. We validate the approach by translating the sensitivity parameter obtained from this method into the CO binding rates in myoglobin upon mutation, resulting in a semi-quantitative correlation with experiments. The model is further validated against an explicit simulation for one of the experimental mutants.
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Affiliation(s)
- David De Sancho
- Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom
- CIC nanoGUNE , Tolosa Hiribidea 76, 20018 Donostia-San Sebastian, Spain
- IKERBASQUE, Basque Foundation for Science , Maria Diaz de Haro 3, 48013 Bilbao, Spain
| | - Adam Kubas
- Department of Physics and Astronomy, University College London , Gower Street, London WC1E 6BT, United Kingdom
| | - Po-Hung Wang
- Department of Physics and Astronomy, University College London , Gower Street, London WC1E 6BT, United Kingdom
- Theoretical Molecular Science Laboratory , 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - Jochen Blumberger
- Department of Physics and Astronomy, University College London , Gower Street, London WC1E 6BT, United Kingdom
| | - Robert B Best
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0520, United States
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19
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Trujillo K, Papagiannopoulos T, Olsen KW. Effects of mutations on the molecular dynamics of oxygen escape from the dimeric hemoglobin of Scapharca inaequivalvis. F1000Res 2015; 4:65. [PMID: 25866622 PMCID: PMC4376171 DOI: 10.12688/f1000research.6127.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/23/2015] [Indexed: 12/15/2022] Open
Abstract
Like many hemoglobins, the structure of the dimeric hemoglobin from the clam
Scapharca inaequivalvis is a “closed bottle” since there is no direct tunnel from the oxygen binding site on the heme to the solvent. The proximal histidine faces the dimer interface, which consists of the E and F helicies. This is significantly different from tetrameric vertebrate hemoglobins and brings the heme groups near the subunit interface. The subunit interface is also characterized by an immobile, hydrogen-bonded network of water molecules. Although there is data which is consistent with the histidine gate pathway for ligand escape, these aspects of the structure would seem to make that pathway less likely. Locally enhanced sampling molecular dynamics are used here to suggest alternative pathways in the wild-type and six mutant proteins. In most cases the point mutations change the selection of exit routes observed in the simulations. Exit via the histidine gate is rarely seem although oxygen molecules do occasionally cross over the interface from one subunit to the other. The results suggest that changes in flexibility and, in some cases, creation of new cavities can explain the effects of the mutations on ligand exit paths.
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Affiliation(s)
- Kevin Trujillo
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, IL, 60660, USA
| | - Tasso Papagiannopoulos
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, IL, 60660, USA
| | - Kenneth W Olsen
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, IL, 60660, USA
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20
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Di Giuseppe AMA, Caso JV, Severino V, Ragucci S, Chambery A, Russo R, Fattorusso R, Ferreras JM, Russo L, Di Maro A. Insight into the structural and functional features of myoglobin from Hystrix cristata L. and Rangifer tarandus L. RSC Adv 2015. [DOI: 10.1039/c5ra01316j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Myoglobins (Mbs) from Hystrix cristata L. and Rangifer tarandus L. have been isolated and characterised.
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Affiliation(s)
- Antonella M. A. Di Giuseppe
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF)
- Second University of Naples
- 81100-Caserta
- Italy
| | - Jolanda V. Caso
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF)
- Second University of Naples
- 81100-Caserta
- Italy
| | - Valeria Severino
- Department of Internal Medicine Specialties
- Geneva University
- 1211-Genève
- Switzerland
| | - Sara Ragucci
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF)
- Second University of Naples
- 81100-Caserta
- Italy
| | - Angela Chambery
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF)
- Second University of Naples
- 81100-Caserta
- Italy
| | - Rosita Russo
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF)
- Second University of Naples
- 81100-Caserta
- Italy
| | - Roberto Fattorusso
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF)
- Second University of Naples
- 81100-Caserta
- Italy
| | - José M. Ferreras
- Department of Biochemistry and Molecular Biology and Physiology
- University of Valladolid
- Campus Miguel Delibes
- 47011-Valladolid
- Spain
| | - Luigi Russo
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF)
- Second University of Naples
- 81100-Caserta
- Italy
| | - Antimo Di Maro
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF)
- Second University of Naples
- 81100-Caserta
- Italy
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21
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Oliveira ASF, Damas JM, Baptista AM, Soares CM. Exploring O2 diffusion in A-type cytochrome c oxidases: molecular dynamics simulations uncover two alternative channels towards the binuclear site. PLoS Comput Biol 2014; 10:e1004010. [PMID: 25474152 PMCID: PMC4256069 DOI: 10.1371/journal.pcbi.1004010] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 10/29/2014] [Indexed: 12/04/2022] Open
Abstract
Cytochrome c oxidases (Ccoxs) are the terminal enzymes of the respiratory chain in mitochondria and most bacteria. These enzymes couple dioxygen (O2) reduction to the generation of a transmembrane electrochemical proton gradient. Despite decades of research and the availability of a large amount of structural and biochemical data available for the A-type Ccox family, little is known about the channel(s) used by O2 to travel from the solvent/membrane to the heme a3-CuB binuclear center (BNC). Moreover, the identification of all possible O2 channels as well as the atomic details of O2 diffusion is essential for the understanding of the working mechanisms of the A-type Ccox. In this work, we determined the O2 distribution within Ccox from Rhodobacter sphaeroides, in the fully reduced state, in order to identify and characterize all the putative O2 channels leading towards the BNC. For that, we use an integrated strategy combining atomistic molecular dynamics (MD) simulations (with and without explicit O2 molecules) and implicit ligand sampling (ILS) calculations. Based on the 3D free energy map for O2 inside Ccox, three channels were identified, all starting in the membrane hydrophobic region and connecting the surface of the protein to the BNC. One of these channels corresponds to the pathway inferred from the X-ray data available, whereas the other two are alternative routes for O2 to reach the BNC. Both alternative O2 channels start in the membrane spanning region and terminate close to Y288I. These channels are a combination of multiple transiently interconnected hydrophobic cavities, whose opening and closure is regulated by the thermal fluctuations of the lining residues. Furthermore, our results show that, in this Ccox, the most likely (energetically preferred) routes for O2 to reach the BNC are the alternative channels, rather than the X-ray inferred pathway. Cytochrome c oxidases (Ccoxs), the terminal enzymes of the respiratory electron transport chain in eukaryotes and many prokaryotes, are key enzymes in aerobic respiration. These proteins couple the reduction of molecular dioxygen to water with the creation of a transmembrane electrochemical proton gradient. Over the last decades, most of the Ccoxs research focused on the mechanisms and energetics of reduction and/or proton pumping, and little emphasis has been given to the pathways used by dioxygen to reach the binuclear center, where dioxygen reduction takes place. In particular, the existence and the characteristics of the channel(s) used by O2 to travel from the solvent/membrane to the binuclear site are still unclear. In this work, we combine all-atom molecular dynamics simulations and implicit ligand sampling calculations in order to identify and characterize the O2 delivery channels in the Ccox from Rhodobacter sphaeroides. Altogether, our results suggest that, in this Ccox, O2 can diffuse via three well-defined channels that start in membrane region (where O2 solubility is higher than in the water). One of these channels corresponds to the pathway inferred from the X-ray data available, whereas the other two are alternative routes for O2 to reach the binuclear center.
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Affiliation(s)
- A. Sofia F. Oliveira
- ITQB - Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - João M. Damas
- ITQB - Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - António M. Baptista
- ITQB - Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Cláudio M. Soares
- ITQB - Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
- * E-mail:
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22
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Zhao J, Srajer V, Franzen S. Functional consequences of the open distal pocket of dehaloperoxidase-hemoglobin observed by time-resolved X-ray crystallography. Biochemistry 2013; 52:7943-50. [PMID: 24116924 DOI: 10.1021/bi401118q] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using time-resolved X-ray crystallography, we contrast a bifunctional dehaloperoxidase-hemoglobin (DHP) with previously studied examples of myoglobin and hemoglobin to understand the functional role of the distal pocket of globins. One key functional difference between DHP and other globins is the requirement that H2O2 enter the distal pocket of oxyferrous DHP to displace O2 from the heme Fe atom and thereby activate the heme for the peroxidase function. The open architecture of DHP permits more than one molecule to simultaneously enter the distal pocket of the protein above the heme to facilitate the unique peroxidase cycle starting from the oxyferrous state. The time-resolved X-ray data show that the distal pocket of DHP lacks a protein valve found in the two other globins that have been studied previously. The photolyzed CO ligand trajectory in DHP does not have a docking site; rather, the CO moves immediately to the Xe-binding site. From there, CO can escape but can also recombine an order of magnitude more rapidly than in other globins. The contrast with DHP dynamics and function more precisely defines the functional role of the multiple conformational states of myoglobin. Taken together with the high reduction potential of DHP, the open distal site helps to explain how a globin can also function as a peroxidase.
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Affiliation(s)
- Junjie Zhao
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
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23
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Abbruzzetti S, Spyrakis F, Bidon-Chanal A, Luque FJ, Viappiani C. Ligand migration through hemeprotein cavities: insights from laser flash photolysis and molecular dynamics simulations. Phys Chem Chem Phys 2013; 15:10686-701. [PMID: 23733145 DOI: 10.1039/c3cp51149a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The presence of cavities and tunnels in the interior of proteins, in conjunction with the structural plasticity arising from the coupling to the thermal fluctuations of the protein scaffold, has profound consequences on the pathways followed by ligands moving through the protein matrix. In this perspective we discuss how quantitative analysis of experimental rebinding kinetics from laser flash photolysis, trapping of unstable conformational states by embedding proteins within the nanopores of silica gels, and molecular simulations can synergistically converge to gain insight into the migration mechanism of ligands. We show how the evaluation of the free energy landscape for ligand diffusion based on the outcome of computational techniques can assist the definition of sound reaction schemes, leading to a comprehensive understanding of the broad range of chemical events and time scales that encompass the transport of small ligands in hemeproteins.
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Affiliation(s)
- Stefania Abbruzzetti
- Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Parma, viale delle Scienze 7A, 43124, Parma, Italy
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24
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Scorciapino MA, Spiga E, Vezzoli A, Mrakic-Sposta S, Russo R, Fink B, Casu M, Gussoni M, Ceccarelli M. Structure–Function Paradigm in Human Myoglobin: How a Single-Residue Substitution Affects NO Reactivity at Low pO2. J Am Chem Soc 2013; 135:7534-44. [DOI: 10.1021/ja400213t] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
| | | | - Alessandra Vezzoli
- Institute for Bioimaging and
Molecular Physiology, Consiglio Nazionale delle Ricerche (CNR), Segrate (MI), Italy
| | - Simona Mrakic-Sposta
- Department of Pathophysiology
and Transplantation−Physiology Section, University of Milan, Milan, Italy
| | - Rosaria Russo
- Department of Pathophysiology
and Transplantation−Physiology Section, University of Milan, Milan, Italy
| | - Bruno Fink
- Noxygen Science Transfer and Diagnostics GmbH, Elzach, Germany
| | | | - Maristella Gussoni
- Department of Pathophysiology
and Transplantation−Physiology Section, University of Milan, Milan, Italy
- Institute for Macromolecular
Studies, CNR, Milan, Italy
| | - Matteo Ceccarelli
- Istituto Officina dei Materiali del Consiglio Nazionale delle Ricerche (IOM-CNR), UOS, Cagliari, Italy
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25
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Takayanagi M, Kurisaki I, Nagaoka M. Oxygen Entry through Multiple Pathways in T-State Human Hemoglobin. J Phys Chem B 2013; 117:6082-91. [DOI: 10.1021/jp401459b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Masayoshi Takayanagi
- Core
Research for Evolutional
Science and Technology, Japan Science and Technology Agency, Honmachi, Kawaguchi 332-0012, Japan
| | - Ikuo Kurisaki
- Core
Research for Evolutional
Science and Technology, Japan Science and Technology Agency, Honmachi, Kawaguchi 332-0012, Japan
| | - Masataka Nagaoka
- Core
Research for Evolutional
Science and Technology, Japan Science and Technology Agency, Honmachi, Kawaguchi 332-0012, Japan
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26
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Oliveira A, Allegri A, Bidon-Chanal A, Knipp M, Roitberg AE, Abbruzzetti S, Viappiani C, Luque FJ. Kinetics and computational studies of ligand migration in nitrophorin 7 and its Δ1-3 mutant. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:1711-21. [PMID: 23624263 DOI: 10.1016/j.bbapap.2013.04.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 03/25/2013] [Accepted: 04/11/2013] [Indexed: 11/18/2022]
Abstract
Nitrophorins (NPs) are nitric oxide (NO)-carrying heme proteins found in the saliva of the blood-sucking insect Rhodnius prolixus. Though NP7 exhibits a large sequence resemblance with other NPs, two major differential features are the ability to interact with negatively charged cell surfaces and the presence of a specific N-terminus composed of three extra residues (Leu1-Pro2-Gly3). The aim of this study is to examine the influence of the N-terminus on the ligand binding, and the topological features of inner cavities in closed and open states of NP7, which can be associated to the protein structure at low and high pH, respectively. Laser flash photolysis measurements of the CO rebinding kinetics to NP7 and its variant NP7(Δ1-3), which lacks the three extra residues at the N-terminus, exhibit a similar pattern and support the existence of a common kinetic mechanism for ligand migration and binding. This is supported by the existence of a common topology of inner cavities, which consists of two docking sites in the heme pocket and a secondary site at the back of the protein. The ligand exchange between these cavities is facilitated by an additional site, which can be transiently occupied by the ligand in NP7, although it is absent in NP4. These features provide a basis to explain the enhanced internal gas hosting capacity found experimentally in NP7 and the absence of ligand rebinding from secondary sites in NP4. The current data allow us to speculate that the processes of docking to cell surfaces and NO release may be interconnected in NP7, thereby efficiently releasing NO into a target cell. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins.
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Affiliation(s)
- Ana Oliveira
- Departament de Fisicoquímica and Institut de Biomedicina, Universitat de Barcelona, Spain
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27
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Boechi L, Arrar M, Martí MA, Olson JS, Roitberg AE, Estrin DA. Hydrophobic effect drives oxygen uptake in myoglobin via histidine E7. J Biol Chem 2013; 288:6754-62. [PMID: 23297402 DOI: 10.1074/jbc.m112.426056] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Since the elucidation of the myoglobin (Mb) structure, a histidine residue on the E helix (His-E7) has been proposed to act as a gate with an open or closed conformation controlling access to the active site. Although it is believed that at low pH, the His-E7 gate is in its open conformation, the full relationship between the His-E7 protonation state, its conformation, and ligand migration in Mb is hotly debated. We used molecular dynamics simulations to first address the effect of His-E7 protonation on its conformation. We observed the expected shift from the closed to the open conformation upon protonation, but more importantly, noted a significant difference between the conformations of the two neutral histidine tautomers. We further computed free energy profiles for oxygen migration in each of the possible His-E7 states as well as in two instructive Mb mutants: Ala-E7 and Trp-E7. Our results show that even in the closed conformation, the His-E7 gate does not create a large barrier to oxygen migration and permits oxygen entry with only a small rotation of the imidazole side chain and movement of the E helix. We identify, instead, a hydrophobic site in the E7 channel that can accommodate an apolar diatomic ligand and enhances ligand uptake particularly in the open His-E7 conformation. This rate enhancement is diminished in the closed conformation. Taken together, our results provide a new conceptual framework for the histidine gate hypothesis.
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Affiliation(s)
- Leonardo Boechi
- Departamento de Química Inorgánica, Analítica, y Química Física/Inquimae-Conicet, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires. Ciudad Universitaria, Pabellon 2, C1428EHA Buenos Aires, Argentina
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28
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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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29
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Bocahut A, Derrien V, Bernad S, Sebban P, Sacquin-Mora S, Guittet E, Lescop E. Heme orientation modulates histidine dissociation and ligand binding kinetics in the hexacoordinated human neuroglobin. J Biol Inorg Chem 2012; 18:111-22. [PMID: 23135388 PMCID: PMC3535368 DOI: 10.1007/s00775-012-0956-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Accepted: 10/21/2012] [Indexed: 11/05/2022]
Abstract
Neuroglobin (Ngb) is a globin present in the brain and retina of mammals. This hexacoordinated hemoprotein binds small diatomic molecules, albeit with lower affinity compared with other globins. Another distinctive feature of most mammalian Ngb is their ability to form an internal disulfide bridge that increases ligand affinity. As often seen for prosthetic heme b containing proteins, human Ngb exhibits heme heterogeneity with two alternative heme orientations within the heme pocket. To date, no details are available on the impact of heme orientation on the binding properties of human Ngb and its interplay with the cysteine oxidation state. In this work, we used 1H NMR spectroscopy to probe the cyanide binding properties of different Ngb species in solution, including wild-type Ngb and the single (C120S) and triple (C46G/C55S/C120S) mutants. We demonstrate that in the disulfide-containing wild-type protein cyanide ligation is fivefold faster for one of the two heme orientations (the A isomer) compared with the other isomer, which is attributed to the lower stability of the distal His64–iron bond and reduced steric hindrance at the bottom of the cavity for heme sliding in the A conformer. We also attribute the slower cyanide reactivity in the absence of a disulfide bridge to the tighter histidine–iron bond. More generally, enhanced internal mobility in the CD loop bearing the disulfide bridge hinders access of the ligand to heme iron by stabilizing the histidine–iron bond. The functional impact of heme disorder and cysteine oxidation state on the properties of the Ngb ligand is discussed.
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Affiliation(s)
- Anthony Bocahut
- Laboratoire de Chimie Physique, UMR 8000, CNRS, Université Paris-Sud 11, Bât. 350, 91405 Orsay, France
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30
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El-Hendawy MM, Garate JA, English NJ, O'Reilly S, Mooney DA. Diffusion and interactions of carbon dioxide and oxygen in the vicinity of the active site of Rubisco: Molecular dynamics and quantum chemical studies. J Chem Phys 2012; 137:145103. [DOI: 10.1063/1.4757021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Affiliation(s)
- Morad M El-Hendawy
- SFI Strategic Research Cluster in Solar Energy Conversion, University College Dublin, Belfield, Dublin 4, Ireland
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31
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Tsuduki T, Tomita A, Koshihara SY, Adachi SI, Yamato T. Ligand migration in myoglobin: a combined study of computer simulation and x-ray crystallography. J Chem Phys 2012; 136:165101. [PMID: 22559505 DOI: 10.1063/1.4704586] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
A ligand-migration mechanism of myoglobin was studied by a multidisciplinary approach that used x-ray crystallography and molecular dynamics simulation. The former revealed the structural changes of the protein along with the ligand migration, and the latter provided the statistical ensemble of protein conformations around the thermal average. We developed a novel computational method, homogeneous ensemble displacement, and generated the conformational ensemble of ligand-detached species from that of ligand-bound species. The thermally averaged ligand-protein interaction was illustrated in terms of the potential of mean force. Although the structural changes were small, the presence of the ligand molecule in the protein matrix significantly affected the 3D scalar field of the potential of mean force, in accordance with the self-opening model proposed in the previous x-ray study.
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Affiliation(s)
- Takayuki Tsuduki
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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32
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Shadrina MS, English AM, Peslherbe GH. Effective Simulations of Gas Diffusion Through Kinetically Accessible Tunnels in Multisubunit Proteins: O2 Pathways and Escape Routes in T-state Deoxyhemoglobin. J Am Chem Soc 2012; 134:11177-84. [DOI: 10.1021/ja300903c] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Maria S. Shadrina
- Department
of Chemistry and Biochemistry and Centre
for Research in Molecular Modeling, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec, Canada H4B 1R6
| | - Ann M. English
- Department
of Chemistry and Biochemistry and Centre
for Research in Molecular Modeling, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec, Canada H4B 1R6
| | - Gilles H. Peslherbe
- Department
of Chemistry and Biochemistry and Centre
for Research in Molecular Modeling, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec, Canada H4B 1R6
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Sgrignani J, Magistrato A. Influence of the Membrane Lipophilic Environment on the Structure and on the Substrate Access/Egress Routes of the Human Aromatase Enzyme. A Computational Study. J Chem Inf Model 2012; 52:1595-606. [DOI: 10.1021/ci300151h] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Jacopo Sgrignani
- CNR-IOM-Democritos National Simulation Center c/o International Studies for Advanced Studies (SISSA/ISAS), via Bonomea 265, 34165 Trieste
(TS), Italy
| | - Alessandra Magistrato
- CNR-IOM-Democritos National Simulation Center c/o International Studies for Advanced Studies (SISSA/ISAS), via Bonomea 265, 34165 Trieste
(TS), Italy
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Forti F, Boechi L, Bikiel D, Martí MA, Nardini M, Bolognesi M, Viappiani C, Estrin D, Luque FJ. Ligand Migration in Methanosarcina acetivorans Protoglobin: Effects of Ligand Binding and Dimeric Assembly. J Phys Chem B 2011; 115:13771-80. [DOI: 10.1021/jp208562b] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Flavio Forti
- Departament de Fisicoquímica and Institut de Biomedicina, Facultat de Farmàcia, Universitat de Barcelona, Avinguda Diagonal 643, E-08028, Barcelona, Spain
| | - Leonardo Boechi
- Departamento de Química Inorgánica, Analítica, y Química Física, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina
| | - Damian Bikiel
- Departamento de Química Inorgánica, Analítica, y Química Física, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina
| | - Marcelo A. Martí
- Departamento de Química Inorgánica, Analítica, y Química Física, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina
| | - Marco Nardini
- Dipartimento di Scienze Biomolecolari e Biotecnologie and CIMAINA, Università degli Studi di Milano, I-20131 Milano, Italy
| | - Martino Bolognesi
- Dipartimento di Scienze Biomolecolari e Biotecnologie and CIMAINA, Università degli Studi di Milano, I-20131 Milano, Italy
| | - Cristiano Viappiani
- Dipartimento di Fisica, Università degli Studi di Parma, Parma, Italy
- NEST, Istituto Nanoscienze-CNR, Italy
| | - Darío Estrin
- Departamento de Química Inorgánica, Analítica, y Química Física, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina
| | - F. Javier Luque
- Departament de Fisicoquímica and Institut de Biomedicina, Facultat de Farmàcia, Universitat de Barcelona, Avinguda Diagonal 643, E-08028, Barcelona, Spain
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35
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Spyrakis F, Bruno S, Bidon-Chanal A, Luque FJ, Abbruzzetti S, Viappiani C, Dominici P, Mozzarelli A. Oxygen binding to Arabidopsis thaliana AHb2 nonsymbiotic hemoglobin: evidence for a role in oxygen transport. IUBMB Life 2011; 63:355-62. [PMID: 21618402 DOI: 10.1002/iub.470] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Nonsymbiotic hemoglobins AHb1 and AHb2 discovered in Arabidopsis thaliana are likely to carry out distinct physiological roles, in consideration of their differences in sequence, structure, expression pattern, and tissue localization. Despite a relatively fast autoxidation in the presence of O(2) , we were able to collect O(2) -binding curves for AHb2 in the presence of a reduction enzymatic system. AHb2 binds O(2) noncooperatively with a p50 of 0.021 ± 0.003 Torr, a value consistent with a recently proposed role in O(2) transport. The analysis of the internal cavities derived from the structures sampled in molecular dynamics simulations confirms strong differences with AHb1, proposed to work as a NO deoxygenase in vivo. Overall, our results are consistent with a role for AHb2 as an oxygen carrier, as recently proposed on the basis of experiments on AHb2-overexpressing mutants of A. thaliana.
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Affiliation(s)
- Francesca Spyrakis
- Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Università degli Studi di Parma, Italy
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36
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Birukou I, Maillett DH, Birukova A, Olson JS. Modulating distal cavities in the α and β subunits of human HbA reveals the primary ligand migration pathway. Biochemistry 2011; 50:7361-74. [PMID: 21793487 DOI: 10.1021/bi200923k] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The free volume in the active site of human HbA plays a crucial role in governing the bimolecular rates of O(2), CO, and NO binding, the fraction of geminate ligand recombination, and the rate of NO dioxygenation by the oxygenated complex. We have decreased the size of the distal pocket by mutating Leu(B10), Val(E11), and Leu(G8) to Phe and Trp and that of other more internal cavities by filling them with Xe at high gas pressures. Increasing the size of the B10 side chain reduces bimolecular rates of ligand binding nearly 5000-fold and inhibits CO geminate recombination due to both reduction of the capture volume in the distal pocket and direct steric hindrance of Fe-ligand bond formation. Phe and Trp(E11) mutations also cause a decrease in distal pocket volume but, at the same time, increase access to the Fe atom because of the loss of the γ2 CH(3) group of the native Val(E11) side chain. The net result of these E11 substitutions is a dramatic increase in the rate of geminate recombination because dissociated CO is sequestered close to the Fe atom and can rapidly rebind without steric resistance. However, the bimolecular rate constants for binding of ligand to the Phe and Trp(E11) mutants are decreased 5-30-fold, because of a smaller capture volume. Geminate and bimolecular kinetic parameters for Phe and Trp(G8) mutants are similar to those for the native HbA subunits because the aromatic rings at this position cause little change in distal pocket volume and because ligands do not move past this position into the globin interior of wild-type HbA subunits. The latter conclusion is verified by the observation that Xe binding to the α and β Hb subunits has little effect on either geminate or bimolecular ligand rebinding. All of these experimental results argue strongly against alternative ligand migration pathways that involve movements through the protein interior in HbA. Instead, ligands appear to enter through the His(E7) gate and are captured directly in the distal cavity.
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Affiliation(s)
- Ivan Birukou
- Department of Biochemistry and Cell Biology and WM Keck Center for Computational Biology, Rice University, Houston, Texas 77005, United States
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37
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Spyrakis F, Luque FJ, Viappiani C. Structural analysis in nonsymbiotic hemoglobins: what can we learn from inner cavities? PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2011; 181:8-13. [PMID: 21600392 DOI: 10.1016/j.plantsci.2011.03.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 03/24/2011] [Accepted: 03/29/2011] [Indexed: 05/09/2023]
Abstract
Plants contain three classes of hemoglobins which are not associated with nitrogen fixing bacteria, and have been accordingly termed nonsymbiotic hemoglobins. The function of nonsymbiotic hemoglobins is as yet mostly unknown. A NO dioxygenase activity has been proposed and demonstrated for some of them in vitro. In this context, a sound molecular mechanism that relates the structure with the biological activity is crucial to suggest a given physiological role. Insight into such a mechanism is now facilitated by recent progress made in both experimental and computational techniques. These studies have highlighted a number of key structural features implicated in the function of nonsymbiotic hemoglobins. The bis-histidyl hexacoordination of the heme in both its ferric and ferrous states provides a powerful and general tool to modulate reactivity, protein dynamics, and shape of the cavities. In addition, the specific arrangement of distal cavity residues provides effective protection against autoxidation. Inspection of the static crystal structures available for both liganded and unliganded states seems unsufficient to explain the function of these proteins. Function appears to be intimately linked with protein flexibility, which influences the dynamical behavior of inner cavities, capable of delivering apolar reactants to the reaction site, and removing charged reaction products. In this mini review, we demonstrate how the integration of information derived from experimental assays and computational studies is valuable and can shed light into the linkage between structural plasticity of nonsymbiotic hemoglobins and their biological role.
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Affiliation(s)
- Francesca Spyrakis
- Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Università degli Studi di Parma, Italy
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38
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Bocahut A, Bernad S, Sebban P, Sacquin-Mora S. Frontier Residues Lining Globin Internal Cavities Present Specific Mechanical Properties. J Am Chem Soc 2011; 133:8753-61. [DOI: 10.1021/ja202587a] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Anthony Bocahut
- Laboratoire de Biochimie Théorique, UMR 9080 CNRS, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Sophie Bernad
- Laboratoire de Chimie Physique, CNRS UMR8000, Bât. 350, Université Paris-sud, 91405 Orsay, France
| | - Pierre Sebban
- Laboratoire de Chimie Physique, CNRS UMR8000, Bât. 350, Université Paris-sud, 91405 Orsay, France
- Université des Sciences et des Technologies de Hanoi, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam
| | - Sophie Sacquin-Mora
- Laboratoire de Biochimie Théorique, UMR 9080 CNRS, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
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39
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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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40
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Spyrakis F, Faggiano S, Abbruzzetti S, Dominici P, Cacciatori E, Astegno A, Droghetti E, Feis A, Smulevich G, Bruno S, Mozzarelli A, Cozzini P, Viappiani C, Bidon-Chanal A, Luque FJ. Histidine E7 dynamics modulates ligand exchange between distal pocket and solvent in AHb1 from Arabidopsis thaliana. J Phys Chem B 2011; 115:4138-46. [PMID: 21428382 DOI: 10.1021/jp110816h] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The distal His residue in type 1 nonsymbiotic hemoglobin AHb1 from Arabidopsis thaliana plays a fundamental role in stabilizing the bound ligand. This residue might also be important in regulating the accessibility to the distal cavity. The feasibility of this functional role has been examined using a combination of experimental and computational methods. We show that the exchange of CO between the solvent and the reaction site is modulated by a swinging motion of the distal His, which opens a channel that connects directly the distal heme pocket with the solvent. The nearby PheB10 aids the distal His in the stabilization of the bound ligand by providing additional protection against solvation. Overall, these findings provide evidence supporting the functional implications of the conformational rearrangement found for the distal His in AHb1, which mimics the gating role proposed for the same residue in myoglobin.
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Affiliation(s)
- Francesca Spyrakis
- Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Università degli Studi di Parma, Italy
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41
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Wang PH, Best RB, Blumberger J. A microscopic model for gas diffusion dynamics in a [NiFe]-hydrogenase. Phys Chem Chem Phys 2011; 13:7708-19. [PMID: 21409188 DOI: 10.1039/c0cp02098b] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
We describe and apply a microscopic model for the calculation of gas diffusion rates in a [NiFe]-hydrogenase. This enzyme has attracted much interest for use as a H(2) oxidising catalyst in biofuel cells, but a major problem is their inhibition by CO and O(2). In our model, the diffusive hopping of gas molecules in the protein interior is coarse grained using a master equation approach with transition rates estimated from equilibrium and non-equilibrium pulling simulations. Propagating the rate matrix in time, we find that the probability for a gas molecule to reach the enzyme active site follows a mono-exponential increase. Fits to a phenomenological rate law give an effective diffusion rate constant for CO that is in very good agreement with experimental measurements. We find that CO prefers to move along the canonical 'hydrophobic' main channel towards the active site, in contrast to O(2) and H(2), which were previously shown to explore larger fractions of the protein. Differences in the diffusion of the three gases are discussed in light of recent efforts to engineer a gas selectivity filter in the enzyme.
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Affiliation(s)
- Po-hung Wang
- Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
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42
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Wang PH, Best RB, Blumberger J. Multiscale simulation reveals multiple pathways for H2 and O2 transport in a [NiFe]-hydrogenase. J Am Chem Soc 2011; 133:3548-56. [PMID: 21341658 DOI: 10.1021/ja109712q] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hydrogenases are enzymes that catalyze the reversible conversion of hydrogen molecules to protons and electrons. The mechanism by which the gas molecules reach the active site is important for understanding the function of the enzyme and may play a role in the selectivity for hydrogen over inhibitor molecules. Here, we develop a general multiscale molecular simulation approach for the calculation of diffusion rates and determination of pathways by which substrate or inhibitor gases can reach the protein active site. Combining kinetic data from both equilibrium simulations and enhanced sampling, we construct a master equation describing the movement of gas molecules within the enzyme. We find that the time-dependent gas population of the active site can be fit to the same phenomenological rate law used to interpret experiments, with corresponding diffusion rates in very good agreement with experimental data. However, in contrast to the conventional picture, in which the gases follow a well-defined hydrophobic tunnel, we find that there is a diverse network of accessible pathways by which the gas molecules can reach the active site. The previously identified tunnel accounts for only about 60% of the total flux. Our results suggest that the dramatic decrease in the diffusion rate for mutations involving the residue Val74 could be in part due to the narrowing of the passage Val74-Arg476, immediately adjacent to the binding site, explaining why mutations of Leu122 had only a negligible effect in experiment. Our method is not specific to the [NiFe]-hydrogenase and should be generally applicable to the transport of small molecules in proteins.
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Affiliation(s)
- Po-hung Wang
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
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43
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Time resolved thermodynamics associated with ligand photorelease in heme peroxidases and globins: Open access channels versus gated ligand release. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1065-76. [PMID: 21278003 DOI: 10.1016/j.bbapap.2011.01.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 01/14/2011] [Accepted: 01/17/2011] [Indexed: 10/18/2022]
Abstract
Heme proteins represent a diverse class of biomolecules responsible for an extremely diverse array of physiological functions including electron transport, monooxygenation, ligand transport and storage, cellular signaling, respiration, etc. An intriguing aspect of these proteins is that such functional diversity is accomplished using a single type of heme macrocycle based upon iron protoporphyrin IX. The functional diversity originates from a delicate balance of inter-molecular interactions within the protein matrix together with well choreographed dynamics that modulate the heme electronic structure as well as ligand entry/exit pathways from the bulk solvent to the active site. Of particular interest are the dynamics and energetics associated with the entry/exit of ligands as this process plays a significant role in regulating the rates of heme protein activity. Time-resolved photoacoustic calorimetry (PAC) has emerged as a powerful tool through which to probe the underlying energetics associated with small molecule dissociation and release to the bulk solvent in heme proteins on time scales from tens of nanoseconds to several microseconds. In this review, the results of PAC studies on various classes of heme proteins are summarized highlighting how different protein structures affect the thermodynamics of ligand migration. This article is part of a Special Issue entitled: Protein Dynamics: Experimental and Computational Approaches.
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44
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Birukou I, Soman J, Olson JS. Blocking the gate to ligand entry in human hemoglobin. J Biol Chem 2010; 286:10515-29. [PMID: 21193395 DOI: 10.1074/jbc.m110.176271] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
His(E7) to Trp replacements in HbA lead to markedly biphasic bimolecular CO rebinding after laser photolysis. For isolated mutant subunits, the fraction of fast phase increases with increasing [CO], suggesting a competition between binding to an open conformation with an empty E7 channel and relaxation to blocked or closed, slowly reacting states. The rate of conformational relaxation of the open state is ∼18,000 s(-1) in α subunits and ∼10-fold faster in β subunits, ∼175,000 s(-1). Crystal structures were determined for tetrameric α(WT)β(Trp-63) HbCO, α(Trp-58)β(WT) deoxyHb, and Trp-64 deoxy- and CO-Mb as controls. In Trp-63(E7) βCO, the indole side chain is located in the solvent interface, blocking entry into the E7 channel. Similar blocked Trp-64(E7) conformations are observed in the mutant Mb crystal structures. In Trp-58(E7) deoxy-α subunits, the indole side chain fills both the channel and the distal pocket, forming a completely closed state. The bimolecular rate constant for CO binding, k'(CO), to the open conformations of both mutant Hb subunits is ∼80-90 μm(-1) s(-1), whereas k'(CO) for the completely closed states is 1000-fold slower, ∼0.08 μm(-1) s(-1). A transient intermediate with k'(CO) ≈ 0.7 μm(-1) s(-1) is observed after photolysis of Trp-63(E7) βCO subunits and indicates that the indole ring blocks the entrance to the E7 channel, as observed in the crystal structures of Trp(E7) deoxyMb and βCO subunits. Thus, either blocking or completely filling the E7 channel dramatically slows bimolecular binding, providing strong evidence that the E7 channel is the major pathway (≥90%) for ligand entry in human hemoglobin.
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Affiliation(s)
- Ivan Birukou
- Department of Biochemistry and Cell Biology and the W. M. Keck Center for Computational Biology, Rice University, Houston, Texas 77005, USA
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45
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Xu J, Yin G, Du W. Distal mutation modulates the heme sliding in mouse neuroglobin investigated by molecular dynamics simulation. Proteins 2010; 79:191-202. [DOI: 10.1002/prot.22872] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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46
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Merlino A, Vergara A, Sica F, Aschi M, Amadei A, Di Nola A, Mazzarella L. Free-Energy Profile for CO Binding to Separated Chains of Human and Trematomus newnesi Hemoglobin: Insights from Molecular Dynamics Simulations and Perturbed Matrix Method. J Phys Chem B 2010; 114:7002-8. [DOI: 10.1021/jp908525s] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Antonello Merlino
- Dipartimento di Chimica, University of Naples “Federico II”, Complesso Universitario Monte S. Angelo, Via Cinthia, I-80126 Naples, Italy, Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, I-80134 Naples, Italy, Dipartimento di Chimica, Ingegneria Chimica e Materiali, University of L’Aquila, Via Vetoio, I-67010, L’Aquila, Italy, Dipartimento di Scienze e Tecnologie Chimiche, University of Rome “Tor Vergata”, Via della Ricerca scientifica 1, I-00133 Roma, Italy, and Dipartimento di Chimica,
| | - Alessandro Vergara
- Dipartimento di Chimica, University of Naples “Federico II”, Complesso Universitario Monte S. Angelo, Via Cinthia, I-80126 Naples, Italy, Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, I-80134 Naples, Italy, Dipartimento di Chimica, Ingegneria Chimica e Materiali, University of L’Aquila, Via Vetoio, I-67010, L’Aquila, Italy, Dipartimento di Scienze e Tecnologie Chimiche, University of Rome “Tor Vergata”, Via della Ricerca scientifica 1, I-00133 Roma, Italy, and Dipartimento di Chimica,
| | - Filomena Sica
- Dipartimento di Chimica, University of Naples “Federico II”, Complesso Universitario Monte S. Angelo, Via Cinthia, I-80126 Naples, Italy, Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, I-80134 Naples, Italy, Dipartimento di Chimica, Ingegneria Chimica e Materiali, University of L’Aquila, Via Vetoio, I-67010, L’Aquila, Italy, Dipartimento di Scienze e Tecnologie Chimiche, University of Rome “Tor Vergata”, Via della Ricerca scientifica 1, I-00133 Roma, Italy, and Dipartimento di Chimica,
| | - Massimiliano Aschi
- Dipartimento di Chimica, University of Naples “Federico II”, Complesso Universitario Monte S. Angelo, Via Cinthia, I-80126 Naples, Italy, Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, I-80134 Naples, Italy, Dipartimento di Chimica, Ingegneria Chimica e Materiali, University of L’Aquila, Via Vetoio, I-67010, L’Aquila, Italy, Dipartimento di Scienze e Tecnologie Chimiche, University of Rome “Tor Vergata”, Via della Ricerca scientifica 1, I-00133 Roma, Italy, and Dipartimento di Chimica,
| | - Andrea Amadei
- Dipartimento di Chimica, University of Naples “Federico II”, Complesso Universitario Monte S. Angelo, Via Cinthia, I-80126 Naples, Italy, Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, I-80134 Naples, Italy, Dipartimento di Chimica, Ingegneria Chimica e Materiali, University of L’Aquila, Via Vetoio, I-67010, L’Aquila, Italy, Dipartimento di Scienze e Tecnologie Chimiche, University of Rome “Tor Vergata”, Via della Ricerca scientifica 1, I-00133 Roma, Italy, and Dipartimento di Chimica,
| | - Alfredo Di Nola
- Dipartimento di Chimica, University of Naples “Federico II”, Complesso Universitario Monte S. Angelo, Via Cinthia, I-80126 Naples, Italy, Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, I-80134 Naples, Italy, Dipartimento di Chimica, Ingegneria Chimica e Materiali, University of L’Aquila, Via Vetoio, I-67010, L’Aquila, Italy, Dipartimento di Scienze e Tecnologie Chimiche, University of Rome “Tor Vergata”, Via della Ricerca scientifica 1, I-00133 Roma, Italy, and Dipartimento di Chimica,
| | - Lelio Mazzarella
- Dipartimento di Chimica, University of Naples “Federico II”, Complesso Universitario Monte S. Angelo, Via Cinthia, I-80126 Naples, Italy, Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, I-80134 Naples, Italy, Dipartimento di Chimica, Ingegneria Chimica e Materiali, University of L’Aquila, Via Vetoio, I-67010, L’Aquila, Italy, Dipartimento di Scienze e Tecnologie Chimiche, University of Rome “Tor Vergata”, Via della Ricerca scientifica 1, I-00133 Roma, Italy, and Dipartimento di Chimica,
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47
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Elber R. Ligand diffusion in globins: simulations versus experiment. Curr Opin Struct Biol 2010; 20:162-7. [PMID: 20116995 PMCID: PMC2854186 DOI: 10.1016/j.sbi.2010.01.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Revised: 01/04/2010] [Accepted: 01/05/2010] [Indexed: 11/15/2022]
Abstract
Computer simulations in molecular biophysics describe in atomic detail the structure, dynamics, and function of biological macromolecules. To assess the quality of these models and to pick up new mechanisms, comparisons with experimental measurements are made. Most comparisons examine thermodynamic and average structural properties. Here we discuss studies of dynamics and fluctuations in a protein. The diffusion of a small ligand between internal cavities in myoglobin, and its escape to solvent are considered. Qualitative and semi-quantitative agreements between experiment and simulation are obtained for the identities of the cavities that physically trap the ligand and for the connections between them. However, experimental and computational 'doors' are at significant variance. Simulations suggest multiple gates while kinetic experiments point to one dominant exit.
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Affiliation(s)
- Ron Elber
- Department of Chemistry and Biochemistry, Institute of Computational Engineering and Sciences (ICES), 1 University Station, ICES, C0200, The University of Texas at Austin, Austin, TX 78712, USA
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Knapp JE, Pahl R, Cohen J, Nichols JC, Schulten K, Gibson QH, Srajer V, Royer WE. Ligand migration and cavities within Scapharca Dimeric HbI: studies by time-resolved crystallo-graphy, Xe binding, and computational analysis. Structure 2010; 17:1494-504. [PMID: 19913484 DOI: 10.1016/j.str.2009.09.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Revised: 08/25/2009] [Accepted: 09/09/2009] [Indexed: 11/19/2022]
Abstract
As in many other hemoglobins, no direct route for migration of ligands between solvent and active site is evident from crystal structures of Scapharca inaequivalvis dimeric HbI. Xenon (Xe) and organic halide binding experiments, along with computational analysis presented here, reveal protein cavities as potential ligand migration routes. Time-resolved crystallographic experiments show that photodissociated carbon monoxide (CO) docks within 5 ns at the distal pocket B site and at more remote Xe4 and Xe2 cavities. CO rebinding is not affected by the presence of dichloroethane within the major Xe4 protein cavity, demonstrating that this cavity is not on the major exit pathway. The crystal lattice has a substantial influence on ligand migration, suggesting that significant conformational rearrangements may be required for ligand exit. Taken together, these results are consistent with a distal histidine gate as one important ligand entry and exit route, despite its participation in the dimeric interface.
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Affiliation(s)
- James E Knapp
- Department of Biochemistry and Molecular Pharmacology, The University of Massachusetts Medical School, Worcester, MA 01605, USA
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Scorciapino MA, Robertazzi A, Casu M, Ruggerone P, Ceccarelli M. Breathing motions of a respiratory protein revealed by molecular dynamics simulations. J Am Chem Soc 2009; 131:11825-32. [PMID: 19653680 DOI: 10.1021/ja9028473] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Internal cavities, which are central to the biological functions of myoglobin, are exploited by gaseous ligands (e.g., O(2), NO, CO, etc.) to migrate inside the protein matrix. At present, it is not clear whether the ligand makes its own way inside the protein or instead the internal cavities are an intrinsic feature of myoglobin. To address this issue, standard molecular dynamics simulations were performed on horse-heart met-myoglobin with no ligand migrating inside the protein matrix. To reveal intrinsic internal pathways, the use of a statistical approach was applied to the cavity calculation, with special emphasis on the major pathway from the distal pocket to Xe1. Our study points out the remarkable dynamical behavior of Xe4, whose "breathing motions" may facilitate migration of ligands through the distal region. Additionally, our results highlight a two-way path for a ligand to diffuse through the proximal region, possibly allowing an alternative route in case Xe1 is occupied. Finally, our approach has led us to the identification of key residues, such as leucines, that may work as switches between cavities.
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Affiliation(s)
- Mariano Andrea Scorciapino
- Department of Chemical Sciences, University of Cagliari, Cittadella Universitaria, I-09042 Monserrato (Ca), Italy
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Relating diffusion along the substrate tunnel and oxygen sensitivity in hydrogenase. Nat Chem Biol 2009; 6:63-70. [DOI: 10.1038/nchembio.276] [Citation(s) in RCA: 159] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Accepted: 10/26/2009] [Indexed: 11/08/2022]
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