1
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Hancock JT. Are Protein Cavities and Pockets Commonly Used by Redox Active Signalling Molecules? PLANTS (BASEL, SWITZERLAND) 2023; 12:2594. [PMID: 37514209 PMCID: PMC10383989 DOI: 10.3390/plants12142594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 06/23/2023] [Accepted: 07/05/2023] [Indexed: 07/30/2023]
Abstract
It has been well known for a long time that inert gases, such as xenon (Xe), have significant biological effects. As these atoms are extremely unlikely to partake in direct chemical reactions with biomolecules such as proteins, lipids, and nucleic acids, there must be some other mode of action to account for the effects reported. It has been shown that the topology of proteins allows for cavities and hydrophobic pockets, and it is via an interaction with such protein structures that inert gases are thought to have their action. Recently, it has been mooted that the relatively inert gas molecular hydrogen (H2) may also have its effects via such a mechanism, influencing protein structures and actions. H2 is thought to also act via interaction with redox active compounds, particularly the hydroxyl radical (·OH) and peroxynitrite (ONOO-), but not nitric oxide (NO·), superoxide anions (O2·-) or hydrogen peroxide (H2O2). However, instead of having a direct interaction with H2, is there any evidence that these redox compounds can also interact with Xe pockets and cavities in proteins, either having an independent effect on proteins or interfering with the action of inert gases? This suggestion will be explored here.
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Affiliation(s)
- John T Hancock
- School of Applied Sciences, University of the West of England, Bristol BS16 1QY, UK
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2
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Powell SM, Thomas LM, Richter-Addo GB. The nitrosoamphetamine metabolite is accommodated in the active site of human hemoglobin: Spectroscopy and crystal structure. J Inorg Biochem 2020; 213:111262. [PMID: 33049600 DOI: 10.1016/j.jinorgbio.2020.111262] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/09/2020] [Accepted: 09/21/2020] [Indexed: 11/17/2022]
Abstract
Amphetamine-based (Amph) drugs are metabolized in humans to their hydroxylamine (AmphNHOH) and nitroso (AmphNO) derivatives. The latter metabolites are known to bind to the Fe centers of cytochrome P450 and other heme enzymes to inhibit their activities. Although these AmphNHOH/AmphNO metabolites are present in vivo, their interactions with the blood protein hemoglobin (Hb) and the muscle protein (Mb) have been largely discounted due to a perception that the relatively small heme active sites of Hb and Mb will not be able to accommodate the large AmphNO group. We report the 2.15 Å resolution X-ray crystal structure of the AmphNO adduct of adult human hemoglobin as the Hb [α-FeIII(H2O)][β-FeII(AmphNO)] derivative. We show that the binding of AmphNO to the β subunit is enabled by an E helix movement and stabilization of ligand binding by H-bonding with the distal His63 residue. We also observe an AmphNHOH group in the Xe2 pocket in close proximity to the α heme site in this derivative. Additionally, UV-vis spectroscopy was used to characterize this and related wt and mutant Mb adducts. Importantly, our X-ray crystal structure of this Hb-nitrosoamphetamine complex represents the first crystal structure of a wild-type heme protein adduct of any amphetamine metabolite. Our results provide a framework for further studies of AmphNHOH/AmphNO interactions with Hb and Mb as viable processes that potentially contribute to the overall biological inorganic chemistry of amphetamine drugs.
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Affiliation(s)
- Samantha M Powell
- Price Family Foundation Institute of Structural Biology, and Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, United States of America
| | - Leonard M Thomas
- Price Family Foundation Institute of Structural Biology, and Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, United States of America
| | - George B Richter-Addo
- Price Family Foundation Institute of Structural Biology, and Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, United States of America.
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3
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The Impact of Electron Correlation on Describing QM/MM Interactions in the Attendant Molecular Dynamics Simulations of CO in Myoglobin. Sci Rep 2020; 10:8539. [PMID: 32444817 PMCID: PMC7244521 DOI: 10.1038/s41598-020-65475-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 05/05/2020] [Indexed: 01/10/2023] Open
Abstract
The impact of the dispersion and electron correlation effects on describing quantum mechanics/molecular mechanics (QM/MM) interactions in QM/MM molecular dynamics (MD) simulations was explored by performing a series of up to 2 ns QM/MM MD simulations on the B states of the myoglobin-carbon monoxide (MbCO) system. The results indicate that both dispersion and electron correlations play significant roles in the simulation of the ratios of two B states (B1/B2), which suggests that the inclusion of the electron correlation effects is essential for accurately modeling the interactions between QM and MM subsystems. We found that the QM/MM interaction energies between the CO and the surroundings statistically present a linear correlation with the electric fields along the CO bond. This indicates that QM/MM interactions can be described by a simple physical model of a dipole with constant moment under the action of the electric fields. The treatment provides us with an accurate and effective approach to account for the electron correlation effects in QM/MM MD simulations.
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4
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Shekhar H, Palaniappan A, Peng T, Lafond M, Moody MR, Haworth KJ, Huang S, McPherson DD, Holland CK. Characterization and Imaging of Lipid-Shelled Microbubbles for Ultrasound-Triggered Release of Xenon. Neurotherapeutics 2019; 16:878-890. [PMID: 31020629 PMCID: PMC6694347 DOI: 10.1007/s13311-019-00733-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Xenon (Xe) is a bioactive gas capable of reducing and stabilizing neurologic injury in stroke. The goal of this work was to develop lipid-shelled microbubbles for xenon loading and ultrasound-triggered release. Microbubbles loaded with either xenon (Xe-MB) or xenon and octafluoropropane (Xe-OFP-MB) (9:1 v/v) were synthesized by high-shear mixing. The size distribution and the frequency-dependent attenuation coefficient of Xe-MB and Xe-OFP-MB were measured using a Coulter counter and a broadband acoustic attenuation spectroscopy system, respectively. The Xe dose was evaluated using gas chromatography/mass spectrometry. The total Xe doses in Xe-MB and Xe-OFP-MB were 113.1 ± 13.5 and 145.6 ± 25.5 μl per mg of lipid, respectively. Co-encapsulation of OFP increased the total xenon dose, attenuation coefficient, microbubble stability (in an undersaturated solution), and shelf life of the agent. Triggered release of gas payload was demonstrated with 6-MHz duplex Doppler and 220-kHz pulsed ultrasound. These results constitute the first step toward the use of lipid-shelled microbubbles for applications such as neuroprotection in stroke.
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Affiliation(s)
- Himanshu Shekhar
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA.
| | - Arunkumar Palaniappan
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA
| | - Tao Peng
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Maxime Lafond
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA
| | - Melanie R Moody
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Kevin J Haworth
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, Ohio, USA
| | - Shaoling Huang
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - David D McPherson
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Christy K Holland
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, Ohio, USA
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5
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Wang XW, Zhang JZH, He X. Ab initio Quantum Mechanics/Molecular Mechanics Molecular Dynamics Simulation of CO in the Heme Distal Pocket of Myoglobin. CHINESE J CHEM PHYS 2017. [DOI: 10.1063/1674-0068/30/cjcp1709169] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Xian-wei Wang
- College of Science, Zhejiang University of Technology, Hangzhou 310023, China
- College of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
- Zhejiang Provincial Collaborative Innovation Center of High-end Laser Manufacturing Equipment, Hangzhou 310014, China
| | - John Z. H. Zhang
- College of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
- NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai 200062, China
- Department of Chemistry, New York University, New York 10003, USA
| | - Xiao He
- College of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
- NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai 200062, China
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6
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Novikov EG, Skakun VV, Borst JW, Visser AJWG. Maximum entropy analysis of polarized fluorescence decay of (E)GFP in aqueous solution. Methods Appl Fluoresc 2017; 6:014001. [PMID: 28858857 DOI: 10.1088/2050-6120/aa898b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The maximum entropy method (MEM) was used for the analysis of polarized fluorescence decays of enhanced green fluorescent protein (EGFP) in buffered water/glycerol mixtures, obtained with time-correlated single-photon counting (Visser et al 2016 Methods Appl. Fluoresc. 4 035002). To this end, we used a general-purpose software module of MEM that was earlier developed to analyze (complex) laser photolysis kinetics of ligand rebinding reactions in oxygen binding proteins. We demonstrate that the MEM software provides reliable results and is easy to use for the analysis of both total fluorescence decay and fluorescence anisotropy decay of aqueous solutions of EGFP. The rotational correlation times of EGFP in water/glycerol mixtures, obtained by MEM as maxima of the correlation-time distributions, are identical to the single correlation times determined by global analysis of parallel and perpendicular polarized decay components. The MEM software is also able to determine homo-FRET in another dimeric GFP, for which the transfer correlation time is an order of magnitude shorter than the rotational correlation time. One important advantage utilizing MEM analysis is that no initial guesses of parameters are required, since MEM is able to select the least correlated solution from the feasible set of solutions.
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Affiliation(s)
- Eugene G Novikov
- Institut Curie-Recherche (INSERM U350), Centre Universitaire, F-91405 Orsay, France. Carl Zeiss Microscopy GmbH, D-07745 Jena, Germany
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7
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Zhang L, Zhang Y, Cheng J, Wang L, Wang X, Zhang M, Gao Y, Hu J, Zhang X, Lü J, Li G, Tai R, Fang H. Inert Gas Deactivates Protein Activity by Aggregation. Sci Rep 2017; 7:10176. [PMID: 28860621 PMCID: PMC5579012 DOI: 10.1038/s41598-017-10678-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 08/14/2017] [Indexed: 11/09/2022] Open
Abstract
Biologically inert gases play important roles in the biological functionality of proteins. However, researchers lack a full understanding of the effects of these gases since they are very chemically stable only weakly absorbed by biological tissues. By combining X-ray fluorescence, particle sizing and molecular dynamics (MD) simulations, this work shows that the aggregation of these inert gases near the hydrophobic active cavity of pepsin should lead to protein deactivation. Micro X-ray fluorescence spectra show that a pepsin solution can contain a high concentration of Xe or Kr after gassing, and that the gas concentrations decrease quickly with degassing time. Biological activity experiments indicate a reversible deactivation of the protein during this gassing and degassing. Meanwhile, the nanoparticle size measurements reveal a higher number of “nanoparticles” in gas-containing pepsin solution, also supporting the possible interaction between inert gases and the protein. Further, MD simulations indicate that gas molecules can aggregate into a tiny bubble shape near the hydrophobic active cavity of pepsin, suggesting a mechanism for reducing their biological function.
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Affiliation(s)
- Lijuan Zhang
- Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai, 201800, China.,Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201204, China
| | - Yuebin Zhang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical physics, Chinese Academy of Sciences, Dalian, 116023, China
| | - Jie Cheng
- Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai, 201800, China.,Division of Physical Biology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China.,University of the Chinese Academy of Sciences, Beijing, 100049, China
| | - Lei Wang
- Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201204, China.,University of the Chinese Academy of Sciences, Beijing, 100049, China.,Institute of Mathematics and Physics, Central South University of Forestry and Technology, Changsha, 410004, China
| | - Xingya Wang
- Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201204, China.,University of the Chinese Academy of Sciences, Beijing, 100049, China
| | - Meng Zhang
- Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai, 201800, China.,Division of Interfacial Water, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Yi Gao
- Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai, 201800, China.,Division of Interfacial Water, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Jun Hu
- Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai, 201800, China.,Division of Physical Biology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Xuehua Zhang
- Soft Matter & Interfaces Group, School of Engineering, RMIT University, Melbourne, VIC 3001, Australia
| | - Junhong Lü
- Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai, 201800, China. .,Division of Physical Biology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China.
| | - Guohui Li
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical physics, Chinese Academy of Sciences, Dalian, 116023, China.
| | - Renzhong Tai
- Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai, 201800, China.,Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201204, China
| | - Haiping Fang
- Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai, 201800, China. .,Division of Interfacial Water, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China.
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8
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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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9
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Lepeshkevich SV, Gilevich SN, Parkhats MV, Dzhagarov BM. Molecular oxygen migration through the xenon docking sites of human hemoglobin in the R-state. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:1110-1121. [DOI: 10.1016/j.bbapap.2016.06.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 06/03/2016] [Accepted: 06/06/2016] [Indexed: 11/25/2022]
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10
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Zhao C, Du W. Dynamic features of carboxy cytoglobin distal mutants investigated by molecular dynamics simulations. J Biol Inorg Chem 2016; 21:251-61. [DOI: 10.1007/s00775-016-1334-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 01/04/2016] [Indexed: 01/08/2023]
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11
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Gee LB, Leontyev I, Stuchebrukhov A, Scott AD, Pelmenschikov V, Cramer SP. Docking and migration of carbon monoxide in nitrogenase: the case for gated pockets from infrared spectroscopy and molecular dynamics. Biochemistry 2015; 54:3314-9. [PMID: 25919807 DOI: 10.1021/acs.biochem.5b00216] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Evidence of a CO docking site near the FeMo cofactor in nitrogenase has been obtained by Fourier transform infrared spectroscopy-monitored low-temperature photolysis. We investigated the possible migration paths for CO from this docking site using molecular dynamics calculations. The simulations support the notion of a gas channel with multiple internal pockets from the active site to the protein exterior. Travel between pockets is gated by the motion of protein residues. Implications for the mechanism of nitrogenase reactions with CO and N2 are discussed.
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Affiliation(s)
- Leland B Gee
- †Department of Chemistry, University of California, Davis, California 95616, United States
| | - Igor Leontyev
- §InterX Inc., Berkeley, California 94710, United States
| | - Alexei Stuchebrukhov
- †Department of Chemistry, University of California, Davis, California 95616, United States
| | - Aubrey D Scott
- †Department of Chemistry, University of California, Davis, California 95616, United States
| | | | - Stephen P Cramer
- †Department of Chemistry, University of California, Davis, California 95616, United States.,‡Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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12
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Yu TQ, Lapelosa M, Vanden-Eijnden E, Abrams CF. Full kinetics of CO entry, internal diffusion, and exit in myoglobin from transition-path theory simulations. J Am Chem Soc 2015; 137:3041-50. [PMID: 25664858 PMCID: PMC5508993 DOI: 10.1021/ja512484q] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We use Markovian milestoning molecular dynamics (MD) simulations on a tessellation of the collective variable space for CO localization in myoglobin to estimate the kinetics of entry, exit, and internal site-hopping. The tessellation is determined by analysis of the free-energy surface in that space using transition-path theory (TPT), which provides criteria for defining optimal milestones, allowing short, independent, cell-constrained MD simulations to provide properly weighted kinetic data. We coarse grain the resulting kinetic model at two levels: first, using crystallographically relevant internal cavities and their predicted interconnections and solvent portals; and second, as a three-state side-path scheme inspired by similar models developed from geminate recombination experiments. We show semiquantitative agreement with experiment on entry and exit rates and in the identification of the so-called "histidine gate" at position 64 through which ≈90% of flux between solvent and the distal pocket passes. We also show with six-dimensional calculations that the minimum free-energy pathway of escape through the histidine gate is a "knock-on" mechanism in which motion of the ligand and the gate are sequential and interdependent. In total, these results suggest that such TPT simulations are indeed a promising approach to overcome the practical time-scale limitations of MD to allow reliable estimation of transition mechanisms and rates among metastable states.
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Affiliation(s)
- Tang-Qing Yu
- Courant Institute of Mathematical Sciences, New York University, New York, New York 10012, United States
| | - Mauro Lapelosa
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Eric Vanden-Eijnden
- Courant Institute of Mathematical Sciences, New York University, New York, New York 10012, United States
| | - Cameron F. Abrams
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
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13
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Abstract
![]()
Myoglobin
(Mb) binds diatomic ligands, like O2, CO,
and NO, in a cavity that is only transiently accessible. Crystallography
and molecular simulations show that the ligands can migrate through
an extensive network of transiently connected cavities but disagree
on the locations and occupancy of internal hydration sites. Here,
we use water 2H and 17O magnetic relaxation
dispersion (MRD) to characterize the internal water molecules in Mb
under physiological conditions. We find that equine carbonmonoxy Mb
contains 4.5 ± 1.0 ordered internal water molecules with a mean
survival time of 5.6 ± 0.5 μs at 25 °C. The likely
locations of these water molecules are the four polar hydration sites,
including one of the xenon-binding cavities, that are fully occupied
in all high-resolution crystal structures of equine Mb. The finding
that water escapes from these sites, located 17–31 Å apart
in the protein, on the same μs time scale suggests a global
exchange mechanism. We propose that this mechanism involves transient
penetration of the protein by H-bonded water chains. Such a mechanism
could play a functional role by eliminating trapped ligands. In addition,
the MRD results indicate that 2 or 3 of the 11 histidine residues
of equine Mb undergo intramolecular hydrogen exchange on a μs
time scale.
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Affiliation(s)
- Shuji Kaieda
- Department of Biophysical Chemistry, Lund University , P.O. Box 124, SE-22100 Lund, Sweden
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14
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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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15
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Lapelosa M, Abrams CF. A computational study of water and CO migration sites and channels inside myoglobin. J Chem Theory Comput 2013; 9:1265-1271. [PMID: 23505344 DOI: 10.1021/ct300862j] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pathways are computed for transport of H2O and CO in myoglobin (Mb), using the single sweep and zero-temperature string methods in a fully atomistic, explicitly solvated model system. Our predictions of sites and barriers in the pathways for CO transport agree with previous studies. For H2O, we predict a binding site in the distal pocket (DP), in agreement with crystallographic observations, and another one close to Leu 29 which explains the importance of this residue in controlling the pocket's hydrophobicity, as well as disordered minima in the largely apolar xenon cavities. In particular, H2O can occupy and transition among the xenon cavities, Xe4, Xe2, and Xe3. Our results support the hypothesis that the thermodynamically most favorable entry/exit portal for H2O is the so-called histidine gate (HG), the same as for CO. This result, along with the observation of water occupation of both DP and apolar Xe cavities, suggest that water and small gas molecules like CO compete for access to the protein interior, and therefore models of gas molecule transport within proteins should also explicitly consider water transport.
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Affiliation(s)
- Mauro Lapelosa
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA, 19104 USA
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16
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Gabba M, Abbruzzetti S, Spyrakis F, Forti F, Bruno S, Mozzarelli A, Luque FJ, Viappiani C, Cozzini P, Nardini M, Germani F, Bolognesi M, Moens L, Dewilde S. CO rebinding kinetics and molecular dynamics simulations highlight dynamic regulation of internal cavities in human cytoglobin. PLoS One 2013; 8:e49770. [PMID: 23308092 PMCID: PMC3537629 DOI: 10.1371/journal.pone.0049770] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 10/12/2012] [Indexed: 12/03/2022] Open
Abstract
Cytoglobin (Cygb) was recently discovered in the human genome and localized in different tissues. It was suggested to play tissue-specific protective roles, spanning from scavenging of reactive oxygen species in neurons to supplying oxygen to enzymes in fibroblasts. To shed light on the functioning of such versatile machinery, we have studied the processes supporting transport of gaseous heme ligands in Cygb. Carbon monoxide rebinding shows a complex kinetic pattern with several distinct reaction intermediates, reflecting rebinding from temporary docking sites, second order recombination, and formation (and dissociation) of a bis-histidyl heme hexacoordinated reaction intermediate. Ligand exit to the solvent occurs through distinct pathways, some of which exploit temporary docking sites. The remarkable change in energetic barriers, linked to heme bis-histidyl hexacoordination by HisE7, may be responsible for active regulation of the flux of reactants and products to and from the reaction site on the distal side of the heme. A substantial change in both protein dynamics and inner cavities is observed upon transition from the CO-liganded to the pentacoordinated and bis-histidyl hexacoordinated species, which could be exploited as a signalling state. These findings are consistent with the expected versatility of the molecular activity of this protein.
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Affiliation(s)
- Matteo Gabba
- Institute of Complex Systems - Molekulare Biophysik (ICS-5) Forschungszentrum Jülich, Jülich, Germany
| | - Stefania Abbruzzetti
- Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Parma, Parma, Italy
| | - Francesca Spyrakis
- Dipartimento di Scienze degli Alimenti, Università degli Studi di Parma, Parma, Italy
- INBB, Biostructures and Biosystems National Institute, Rome, Italy
| | - Flavio Forti
- Departament de Fisicoquímica and Institut de Biomedicina (IBUB), Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Spain
| | - Stefano Bruno
- Dipartimento di Farmacia, Università degli Studi di Parma, Parma, Italy
| | - Andrea Mozzarelli
- Dipartimento di Farmacia, Università degli Studi di Parma, Parma, Italy
| | - F. Javier Luque
- Departament de Fisicoquímica and Institut de Biomedicina (IBUB), Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Spain
| | - Cristiano Viappiani
- Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Parma, Parma, Italy
- NEST, Istituto Nanoscienze-CNR, Pisa, Italy
- * E-mail:
| | - Pietro Cozzini
- Dipartimento di Scienze degli Alimenti, Università degli Studi di Parma, Parma, Italy
- INBB, Biostructures and Biosystems National Institute, Rome, Italy
| | - Marco Nardini
- Dipartimento di BioScienze, CNR-IBF, and CIMAINA, Università degli Studi di Milano, Milano, Italy
| | - Francesca Germani
- Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Martino Bolognesi
- Dipartimento di BioScienze, CNR-IBF, and CIMAINA, Università degli Studi di Milano, Milano, Italy
| | - Luc Moens
- Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Sylvia Dewilde
- Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
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Cao Q, Andrijchenko N, Ahola AE, Domanskaya A, Räsänen M, Ermilov A, Nemukhin A, Khriachtchev L. Interaction of phenol with xenon and nitrogen: Spectroscopic and computational characterization. J Chem Phys 2012; 137:134305. [DOI: 10.1063/1.4754435] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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18
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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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19
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Lin TL, Song G. Efficient mapping of ligand migration channel networks in dynamic proteins. Proteins 2011; 79:2475-90. [DOI: 10.1002/prot.23071] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 04/01/2011] [Accepted: 04/19/2011] [Indexed: 11/07/2022]
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20
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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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21
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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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23
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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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24
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Schmidt M, Graber T, Henning R, Srajer V. Five-dimensional crystallography. Acta Crystallogr A 2010; 66:198-206. [PMID: 20164643 PMCID: PMC2824529 DOI: 10.1107/s0108767309054166] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Accepted: 12/15/2009] [Indexed: 11/23/2022] Open
Abstract
Here it is demonstrated how five-dimensional crystallography can be used to determine a comprehensive chemical kinetic mechanism in concert with the atomic structures of transient intermediates that form and decay during the course of the reaction. A method for determining a comprehensive chemical kinetic mechanism in macromolecular reactions is presented. The method is based on five-dimensional crystallography, where, in addition to space and time, temperature is also taken into consideration and an analysis based on singular value decomposition is applied. First results of such a time-resolved crystallographic study are presented. Temperature-dependent time-resolved X-ray diffraction measurements were conducted on the newly upgraded BioCARS 14-ID-B beamline at the Advanced Photon Source and aimed at elucidating a comprehensive kinetic mechanism of the photoactive yellow protein photocycle. Extensive time series of crystallographic data were collected at two temperatures, 293 K and 303 K. Relaxation times of the reaction extracted from these time series exhibit measurable differences for the two temperatures, hence demonstrating that five-dimensional crystallography is feasible.
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Affiliation(s)
- Marius Schmidt
- Physics Department, University of Wisconsin-Milwaukee, Milwaukee, WI, USA.
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25
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Bettati S, Viappiani C, Mozzarelli A. Hemoglobin, an “evergreen” red protein. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1794:1317-24. [DOI: 10.1016/j.bbapap.2009.03.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Accepted: 03/23/2009] [Indexed: 10/20/2022]
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26
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Anedda R, Era B, Casu M, Fais A, Ceccarelli M, Corda M, Ruggerone P. Evidences of xenon-induced structural changes in the active site of cyano-metmyoglobins: a 1H NMR study. J Phys Chem B 2009; 112:15856-66. [PMID: 19368018 DOI: 10.1021/jp807959u] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Using xenon atoms as a biomolecular probe raises the concern of whether they may influence in some way the molecular and electronic structure of the system under study. In this paper, the relevance of guest-host interactions in xenon complexes with paramagnetic myoglobins (Mbs) is thoroughly analyzed, and the issue about the use of xenon to detect and characterize voids within flexible biomolecules is critically discussed. A detailed 1H NMR study useful for describing the hydrophobic cavities close to the active site of low-spin ferric myoglobins with respect to their interaction with the xenon atom is presented. The method is subsequently validated by the analysis of Xe-Mb with two different myoglobins, extracted from horse and pig. These myoglobins differ by 14 amino acids. One of these, Ile142 in horse Mb, is located in the proximal cavity, which is the main xenon binding site in horse Mb, and is replaced by Met142 in pig Mb. We demonstrated specific behaviors associated with the capacity of each of the two myoglobins to bind xenon and provided site-specific information on the host-guest interaction. Moreover, 1H NMR measurements produce a picture of xenon-related local distortions of the protein, associated with a functionally relevant residue located right at the active site, the proximal hystidine E7(His93). According to the 1H NMR data, xenon induces the tilt of the residue His93 relative to the heme plane and consequently causes an alteration of the magnetic axes. Similar conclusions are obtained both for pig cyano-myoglobin and for horse cyano-myoglobin, the structural deformation being in the former of minor entity.
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Affiliation(s)
- Roberto Anedda
- Department of Chemical Sciences, University of Cagliari, Monserrato-Sestu Km 0.700 1-09042, Monserrato, CA, Italy
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27
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Hayakawa N, Kasahara T, Hasegawa D, Yoshimura K, Murakami M, Kouyama T. Effect of Xenon Binding to a Hydrophobic Cavity on the Proton Pumping Cycle in Bacteriorhodopsin. J Mol Biol 2008; 384:812-23. [PMID: 18930734 DOI: 10.1016/j.jmb.2008.09.075] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 09/21/2008] [Accepted: 09/25/2008] [Indexed: 11/25/2022]
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28
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Ronda L, Abbruzzetti S, Bruno S, Bettati S, Mozzarelli A, Viappiani C. Ligand-Induced Tertiary Relaxations During the T-to-R Quaternary Transition in Hemoglobin. J Phys Chem B 2008; 112:12790-4. [DOI: 10.1021/jp803040j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Luca Ronda
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, CNISM, and Dipartimento di Fisica, Università degli Studi di Parma, CNISM, and NEST CNR-INFM
| | - Stefania Abbruzzetti
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, CNISM, and Dipartimento di Fisica, Università degli Studi di Parma, CNISM, and NEST CNR-INFM
| | - Stefano Bruno
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, CNISM, and Dipartimento di Fisica, Università degli Studi di Parma, CNISM, and NEST CNR-INFM
| | - Stefano Bettati
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, CNISM, and Dipartimento di Fisica, Università degli Studi di Parma, CNISM, and NEST CNR-INFM
| | - Andrea Mozzarelli
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, CNISM, and Dipartimento di Fisica, Università degli Studi di Parma, CNISM, and NEST CNR-INFM
| | - Cristiano Viappiani
- Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, CNISM, and Dipartimento di Fisica, Università degli Studi di Parma, CNISM, and NEST CNR-INFM
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Brindell M, Stawoska I, Orzeł L, Labuz P, Stochel G, van Eldik R. Application of high pressure laser flash photolysis in studies on selected hemoprotein reactions. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:1481-92. [PMID: 18778796 DOI: 10.1016/j.bbapap.2008.08.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 07/14/2008] [Accepted: 08/04/2008] [Indexed: 12/31/2022]
Abstract
This article focuses on the application of high pressure laser flash photolysis for studies on selected hemoprotein reactions with the objective to establish details of the underlying reaction mechanisms. In this context, particular attention is given to the reactions of small molecules such as dioxygen, carbon monoxide, and nitric oxide with selected hemoproteins (hemoglobin, myoglobin, neuroglobin and cytochrome P450(cam)), as well as to photo-induced electron transfer reactions occurring in hemoproteins (particularly in various types of cytochromes). Mechanistic conclusions based on the interpretation of the obtained activation volumes are discussed in this account.
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Affiliation(s)
- Małgorzata Brindell
- Department of Inorganic Chemistry, Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow, Poland
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Abbruzzetti S, Bruno S, Faggiano S, Ronda L, Grandi E, Mozzarelli A, Viappiani C. Characterization of ligand migration mechanisms inside hemoglobins from the analysis of geminate rebinding kinetics. Methods Enzymol 2008; 437:329-45. [PMID: 18433636 DOI: 10.1016/s0076-6879(07)37017-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
The presence of internal hydrophobic cavities and packing defects has been demonstrated for several small globular proteins, including hemoglobins. The reduced thermodynamic stability appears to be compensated for by the capability of controlling ligand diffusion through the protein matrix to the active site, possibly by stocking more than one reactant molecule in selected sites. Photolysis of carbon monoxide complexes of hemoglobins encapsulated in silica gels leads to multiphasic geminate rebinding kinetics at room temperature, reflecting rebinding also from different temporary docking sites inside the protein matrix. A careful analysis of the ligand rebinding kinetics allows the determination of the microscopic rates for the underlying reactions, including those governing the migration to and from the docking sites. This chapter describes the experimental approach used to characterize the ligand rebinding kinetics for heme proteins in silica gels after nanosecond laser flash photolysis and the computational methods necessary to retrieve the kinetic parameters.
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Atomic level computational identification of ligand migration pathways between solvent and binding site in myoglobin. Proc Natl Acad Sci U S A 2008; 105:9204-9. [PMID: 18599444 DOI: 10.1073/pnas.0710825105] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Myoglobin is a globular protein involved in oxygen storage and transport. No consensus yet exists on the atomic level mechanism by which oxygen and other small nonpolar ligands move between the myoglobin's buried heme, which is the ligand binding site, and surrounding solvent. This study uses room temperature molecular dynamics simulations to provide a complete atomic level picture of ligand migration in myoglobin. Multiple trajectories--providing a cumulative total of 7 micros of simulation--are analyzed. Our simulation results are consistent with and tie together previous experimental findings. Specifically, we characterize: (i) Explicit full trajectories in which the CO ligand shuttles between the internal binding site and the solvent and (ii) pattern and structural origins of transient voids available for ligand migration. The computations are performed both in sperm whale myoglobin wild-type and in sperm whale V68F myoglobin mutant, which is experimentally known to slow ligand-binding kinetics. On the basis of these independent, but mutually consistent ligand migration and transient void computations, we find that there are two discrete dynamical pathways for ligand migration in myoglobin. Trajectory hops between these pathways are limited to two bottleneck regions. Ligand enters and exits the protein matrix in common identifiable portals on the protein surface. The pathways are located in the "softer" regions of the protein matrix and go between its helices and in its loop regions. Localized structural fluctuations are the primary physical origin of the simulated CO migration pathways inside the protein.
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Use of the Conjugate Peak Refinement Algorithm for Identification of Ligand‐Binding Pathways in Globins. Methods Enzymol 2008; 437:417-37. [DOI: 10.1016/s0076-6879(07)37021-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Ceccarelli M, Anedda R, Casu M, Ruggerone P. CO escape from myoglobin with metadynamics simulations. Proteins 2007; 71:1231-6. [DOI: 10.1002/prot.21817] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Abbruzzetti S, Grandi E, Bruno S, Faggiano S, Spyrakis F, Mozzarelli A, Cacciatori E, Dominici P, Viappiani C. Ligand migration in nonsymbiotic hemoglobin AHb1 from Arabidopsis thaliana. J Phys Chem B 2007; 111:12582-90. [PMID: 17924689 DOI: 10.1021/jp074954o] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AHb1 is a hexacoordinated type 1 nonsymbiotic hemoglobin recently discovered in Arabidopsis thaliana. To gain insight into the ligand migration inside the protein, we studied the CO rebinding kinetics of AHb1 encapsulated in silica gels, in the presence of glycerol. The CO rebinding kinetics after nanosecond laser flash photolysis exhibits complex ligand migration patterns, consistent with the existence of discrete docking sites in which ligands can temporarily be stored before rebinding to the heme at different times. This finding may be of relevance to the physiological NO dioxygenase activity of this protein, which requires sequential binding of two substrates, NO and O2, to the heme.
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Affiliation(s)
- Stefania Abbruzzetti
- Dipartimento di Fisica, Università degli Studi di Parma, NEST CNR-INFM, Parma, Italy
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Samuni U, Dantsker D, Roche C, Friedman JM. Ligand recombination and a hierarchy of solvent slaved dynamics: the origin of kinetic phases in hemeproteins. Gene 2007; 398:234-48. [PMID: 17570619 PMCID: PMC1975397 DOI: 10.1016/j.gene.2007.04.032] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Ligand recombination studies play a central role both for characterizing different hemeproteins and their conformational states but also for probing fundamental biophysical processes. Consequently, there is great importance to providing a foundation from which one can understand the physical processes that give rise to and modulate the large range of kinetic patterns associated with ligand recombination in myoglobins and hemoglobins. In this work, an overview of cryogenic and solution phase recombination phenomena for COMb is first reviewed and then a new paradigm is presented for analyzing the temperature and viscosity dependent features of kinetic traces in terms of multiple phases that reflect which tier(s) of solvent slaved protein dynamics is (are) operative on the photoproduct population during the time course of the measurement. This approach allows for facile inclusion of both ligand diffusion among accessible cavities and conformational relaxation effects. The concepts are illustrated using kinetic traces and MEM populations derived from the CO recombination process for wild type and mutant myoglobins either in sol-gel matrices bathed in glycerol or in trehalose-derived glassy matrices.
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Affiliation(s)
- Uri Samuni
- Albert Einstein College of Medicine, Department of Physiology and Biophysics, Bronx, New York 10461, USA
| | - David Dantsker
- Albert Einstein College of Medicine, Department of Physiology and Biophysics, Bronx, New York 10461, USA
| | - Camille Roche
- Albert Einstein College of Medicine, Department of Physiology and Biophysics, Bronx, New York 10461, USA
| | - Joel M. Friedman
- Albert Einstein College of Medicine, Department of Physiology and Biophysics, Bronx, New York 10461, USA
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Belogortseva N, Rubio M, Terrell W, Miksovská J. The contribution of heme propionate groups to the conformational dynamics associated with CO photodissociation from horse heart myoglobin. J Inorg Biochem 2007; 101:977-86. [PMID: 17499362 DOI: 10.1016/j.jinorgbio.2007.03.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Revised: 03/09/2007] [Accepted: 03/14/2007] [Indexed: 11/26/2022]
Abstract
Photoacoustic calorimetry and transient absorption spectroscopy were used to study conformational dynamics associated with CO photodissociation from horse heart myoglobin (Mb) reconstituted with either Fe protoporphyrin IX dimethylester (FePPDME), Fe octaethylporphyrin (FeOEP), or with native Fe protoporphyrin IX (FePPIX). The volume and enthalpy changes associated with the Fe-CO bond dissociation and formation of a transient deoxyMb intermediate for the reconstituted Mbs were found to be similar to those determined for native Mb (DeltaV1 = -2.5+/-0.6 ml mol(-1) and DeltaH1 = 8.1+/-3.0 kcal mol(-1)). The replacement of FePPIX by FeOEP significantly alters the conformational dynamics associated with CO release from protein. Ligand escape from FeOEP reconstituted Mb was determined to be roughly a factor of two faster (tau=330 ns) relative to native protein (tau=700 ns) and accompanying reaction volume and enthalpy changes were also found to be smaller (DeltaV2 = 5.4+/-2.5 ml mol(-1) and DeltaH2 = 0.7+/-2.2 kcal mol(-1)) than those for native Mb (DeltaV2 = 14.3+/-0.8 ml mol(-1) and DeltaH2 = 7.8+/-3.5 kcal mol(-1)). On the other hand, volume and enthalpy changes for CO release from FePPIX or FePPDME reconstituted Mb were nearly identical to those of the native protein. These results suggest that the hydrogen bonding network between heme propionate groups and nearby amino acid residues likely play an important role in regulating ligand diffusion through protein matrix. Disruption of this network leads to a partially open conformation of protein with less restricted ligand access to the heme binding pocket.
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Affiliation(s)
- Natalia Belogortseva
- Chemistry Department, Marshall University, One John Marshall Drive, Huntington, WV 25755, USA
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Sottini S, Abbruzzetti S, Viappiani C, Ronda L, Mozzarelli A. Determination of microscopic rate constants for CO binding and migration in myoglobin encapsulated in silica gels. J Phys Chem B 2007; 109:19523-8. [PMID: 16853522 DOI: 10.1021/jp054098l] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
CO rebinding kinetics after nanosecond photolysis of myoglobin encapsulated in wet silica gels exhibits an enhanced geminate phase that allows the determination of the microscopic rate constants and the activation barriers for distinct ligand docking sites inside the protein matrix. Using a maximum entropy method, we demonstrate that the geminate phase can be well-described by a biphasic lifetime distribution, reflecting rebinding from the distal and proximal sites. Microscopic rates and activation barriers were estimated using a four-state model.
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Affiliation(s)
- Silvia Sottini
- Dipartimento di Fisica, Università degli Studi di Parma, Parco Area delle Scienze 7/A, Università degli Studi di Parma, Parco Area delle Scienze 23/A, 43100 Parma, Italy
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38
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Mouawad L, Tetreau C, Abdel-Azeim S, Perahia D, Lavalette D. CO migration pathways in cytochrome P450cam studied by molecular dynamics simulations. Protein Sci 2007; 16:781-94. [PMID: 17400927 PMCID: PMC2206643 DOI: 10.1110/ps.062374707] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Previous laser flash photolysis investigations between 100 and 300 K have shown that the kinetics of CO rebinding with cytochrome P450(cam)(camphor) consist of up to four different processes revealing a complex internal dynamics after ligand dissociation. In the present work, molecular dynamics simulations were undertaken on the ternary complex P450(cam)(cam)(CO) to explore the CO migration pathways, monitor the internal cavities of the protein, and localize the CO docking sites. One trajectory of 1 nsec with the protein in a water box and 36 trajectories of 1 nsec in the vacuum were calculated. In each trajectory, the protein contained only one CO ligand on which no constraints were applied. The simulations were performed at 200, 300, and 320 K. The results indicate the presence of seven CO docking sites, mainly hydrophobic, located in the same moiety of the protein. Two of them coincide with xenon binding sites identified by crystallography. The protein matrix exhibits eight persistent internal cavities, four of which corresponding to the ligand docking sites. In addition, it was observed that water molecules entering the protein were mainly attracted into the polar pockets, far away from the CO docking sites. Finally, the identified CO migration pathways provide a consistent interpretation of the experimental rebinding kinetics.
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Affiliation(s)
- Liliane Mouawad
- Inserm U759, Institut Curie-Recherche, Bâtiment 112, Université Paris-Sud, 91405 Orsay cedex, France.
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39
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Naftalin RJ, Green N, Cunningham P. Lactose permease H+-lactose symporter: mechanical switch or Brownian ratchet? Biophys J 2007; 92:3474-91. [PMID: 17325012 PMCID: PMC1853157 DOI: 10.1529/biophysj.106.100669] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Lactose permease structure is deemed consistent with a mechanical switch device for H(+)-coupled symport. Because the crystallography-assigned docking position of thiodigalactoside (TDG) does not make close contact with several amino acids essential for symport; the switch model requires allosteric interactions between the proton and sugar binding sites. The docking program, Autodock 3 reveals other lactose-docking sites. An alternative cotransport mechanism is proposed where His-322 imidazolium, positioned in the central pore equidistant (5-7 A) between six charged amino acids, Arg-302 and Lys-319 opposing Glu-269, Glu-325, Asp-237, and Asp-240, transfers a proton transiently to an H-bonded lactose hydroxyl group. Protonated lactose and its dissociation product H(3)O+ are repelled by reprotonated His-322 and drift in the electrostatic field toward the cytosol. This Brownian ratchet model, unlike the conventional carrier model, accounts for diminished symport by H322N mutant; how H322 mutants become uniporters; why exchanging Lys-319 with Asp-240 paradoxically inactivates symport; how some multiple mutants become revertant transporters; the raised export rate and affinity toward lactose of uncoupled mutants; the altered specificity toward lactose, melibiose, and galactose of some mutants, and the proton dissociation rate of H322 being 100-fold faster than the symport turnover rate.
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Affiliation(s)
- Richard J Naftalin
- King's College London, Physiology Division, Franklin-Wilkins Building, London, United Kingdom.
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40
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Lavalette D, Tétreau C, Mouawad L. Ligand migration and escape pathways in haem proteins. Biochem Soc Trans 2006; 34:975-8. [PMID: 17052240 DOI: 10.1042/bst0340975] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Biophysical techniques developed during the last three decades have provided an increasingly detailed description of the internal processes associated with ligand capture and release by haem proteins. Myoglobin has long been the paradigm for these studies. More recently, cytochrome P450cam (the camphor-metabolizing cytochrome P450 from Pseudomonas putida) has also received considerable interest. In spite of sharing the same prosthetic group, the Fe(II)-haem, these proteins are structurally unrelated and they perform different functions. Recent works show that both proteins exhibit a common feature: a series of permanent or fluctuating, mostly hydrophobic, cavities of the protein matrix are providing transient docking sites as well as migration, escape and possibly entry pathways for the ligand. Remarkably, these systems of cavities connect the distal and the proximal regions of the haem, a disposition that may contribute to ligand capture enhancement.
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Affiliation(s)
- D Lavalette
- Institut Curie, Centre Universitaire, 91405 Orsay, France.
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41
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Abbruzzetti S, Bruno S, Faggiano S, Grandi E, Mozzarelli A, Viappiani C. Time-resolved methods in Biophysics. 2. Monitoring haem proteins at work with nanosecond laser flash photolysis. Photochem Photobiol Sci 2006; 5:1109-20. [PMID: 17136275 DOI: 10.1039/b610236k] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Haem proteins have long been the most studied proteins in biophysics, and have become paradigms for the characterization of fundamental biomolecular processes as ligand binding and regulatory conformational transitions. The presence of the haem prosthetic group, the absorbance spectrum of which has a ligation sensitive region conveniently located in the UV-visible range, has offered a powerful and sensitive tool for the investigation of molecular functions. The central Fe atom is capable of reversibly binding diatomic ligands, including O(2), CO, and NO. The Fe-ligand bond is photolabile, and a reactive unligated state can be transiently generated with a pulsed laser. The photodissociated ligands quickly rebind to the haem and the process can be monitored by transient absorbance methods. The ligand rebinding kinetics reflects protein dynamics and ligand migration within the protein inner cavities. The characterization of these processes was done in the past mainly by low temperature experiments. The use of silica gels to trap proteins allows the characterization of internal ligand dynamics at room temperature. In order to show the potential of the laser flash photolysis techniques, combined with modern numerical analysis methods, we report experiments conducted on two non-symbiotic haemoglobins from Arabidopsis thaliana. The comparison between time courses recorded on haemoglobins in solution and encapsulated in silica gels allows for the highlighting of different interplays between protein dynamics and ligand migration.
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42
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Ye X, Yu A, Champion PM. Dynamics of nitric oxide rebinding and escape in horseradish peroxidase. J Am Chem Soc 2006; 128:1444-5. [PMID: 16448103 PMCID: PMC2768277 DOI: 10.1021/ja057172m] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ultrafast kinetic measurements of NO rebinding to horseradish peroxidase (HRP) are reported for the first time. The geminate kinetics are found to be exponential for all HRP samples studied. The ferric forms of HRP have NO geminate recombination time constants in the range of 15-30 ps, while the ferrous form has a time constant of approximately 7 ps. The simple exponential NO geminate kinetics found for HRP demonstrate that heme relaxation is not the underlying source of the nonexponential NO rebinding in myoglobin (Mb). The NO ligand escape rates from HRP are also determined, and they are found to depend dramatically on the presence or absence of the competitive inhibitor benzohydroxamic acid (BHA). The kinetic results indicate that, in contrast to Mb, there is direct solvent access to the distal heme pocket of HRP.
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43
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Sottini S, Abbruzzetti S, Spyrakis F, Bettati S, Ronda L, Mozzarelli A, Viappiani C. Geminate rebinding in R-state hemoglobin: kinetic and computational evidence for multiple hydrophobic pockets. J Am Chem Soc 2006; 127:17427-32. [PMID: 16332093 DOI: 10.1021/ja056101k] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Biphasic geminate rebinding of CO to myoglobin upon flash photolysis has been associated to ligand distribution in hydrophobic cavities, structurally detected by time-resolved crystallography, xenon occupancy, and molecular simulations. We show that the time course of CO rebinding to human hemoglobin also exhibits a biphasic geminate rebinding when the protein is entrapped in wet nanoporous silica gel. A simple branched kinetic scheme, involving the bound state A, the primary docking site C, and a secondary binding site B was used to calculate the microscopic rates and the time-dependent population of the intermediate species. The activation enthalpies of the associated transitions were determined in the absence and presence of 80% glycerol. Potential hydrophobic docking cavities within the alpha and beta chains of hemoglobin were identified by computational modeling using xenon as a probe. A hydrophobic pocket on the distal side of the heme, corresponding to Xe4 in Mb, and a nearby site that does not have a correspondence in Mb were detected. Neither potential xenon sites on the proximal side nor a migration channel from the distal to proximal site was located. The small enthalpic barriers between states B and C are in very good agreement with the location of the xenon sites on the distal side. Furthermore, the connection between the two xenon sites is relatively open, explaining why the decreased mobility of the protein with viscosity only slightly perturbs the energetics of ligand migration between the two sites.
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Affiliation(s)
- Silvia Sottini
- Dipartimento di Fisica, Università degli Studi di Parma, Parco Area delle Scienze 7/A, 43100 Parma, Italy
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44
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Goldbeck RA, Bhaskaran S, Ortega C, Mendoza JL, Olson JS, Soman J, Kliger DS, Esquerra RM. Water and ligand entry in myoglobin: assessing the speed and extent of heme pocket hydration after CO photodissociation. Proc Natl Acad Sci U S A 2006; 103:1254-9. [PMID: 16432219 PMCID: PMC1360539 DOI: 10.1073/pnas.0507840103] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A previously undescribed spectrokinetic assay for the entry of water into the distal heme pocket of wild-type and mutant myoglobins is presented. Nanosecond photolysis difference spectra were measured in the visible bands of sperm whale myoglobin as a function of distal pocket mutation and temperature. A small blue shift in the 560-nm deoxy absorption peak marked water entry several hundred nanoseconds after CO photodissociation. The observed rate suggests that water entry is rate-limited by the escape of internal dissociated CO. The heme pocket hydration and geminate recombination yields were found to be the primary factors controlling the overall bimolecular association rate constants for CO binding to the mutants studied. The kinetic analysis provides estimates of 84%, 60%, 40%, 0%, and 99% for the steady-state hydrations of wild-type, H64Q, H64A, H64L, and V68F deoxymyoglobin, respectively. The second-order rate constants for CO and H(2)O entry into the empty distal pocket of myoglobin are markedly different, 8 x 10(7) and 2 x 10(5) M(-1).s(-1), respectively, suggesting that hydrophobic partitioning of the apolar gas from the aqueous phase into the relatively apolar protein interior lowers the free energy barrier for CO entry.
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Affiliation(s)
- Robert A Goldbeck
- Department of Chemistry and Biochemistry, University of California-Santa Cruz, Santa Cruz, CA 95064, USA.
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45
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Gensch T, Viappiani C. Introducing the Time-resolved methods in biophysics series. Photochem Photobiol Sci 2006; 5:1101-2. [PMID: 17136273 DOI: 10.1039/b615863n] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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46
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Ionascu D, Gruia F, Ye X, Yu A, Rosca F, Beck C, Demidov A, Olson JS, Champion PM. Temperature-dependent studies of NO recombination to heme and heme proteins. J Am Chem Soc 2005; 127:16921-34. [PMID: 16316238 PMCID: PMC2553725 DOI: 10.1021/ja054249y] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The rebinding kinetics of NO to the heme iron of myoglobin (Mb) is investigated as a function of temperature. Below 200 K, the transition-state enthalpy barrier associated with the fastest (approximately 10 ps) recombination phase is found to be zero and a slower geminate phase (approximately 200 ps) reveals a small enthalpic barrier (approximately 3 +/- 1 kJ/mol). Both of the kinetic rates slow slightly in the myoglobin (Mb) samples above 200 K, suggesting that a small amount of protein relaxation takes place above the solvent glass transition. When the temperature dependence of the NO recombination in Mb is studied under conditions where the distal pocket is mutated (e.g., V68W), the rebinding kinetics lack the slow phase. This is consistent with a mechanism where the slower (approximately 200 ps) kinetic phase involves transitions of the NO ligand into the distal heme pocket from a more distant site (e.g., in or near the Xe4 cavity). Comparison of the temperature-dependent NO rebinding kinetics of native Mb with that of the bare heme (PPIX) in glycerol reveals that the fast (enthalpically barrierless) NO rebinding process observed below 200 K is independent of the presence or absence of the proximal histidine ligand. In contrast, the slowing of the kinetic rates above 200 K in MbNO disappears in the absence of the protein. Generally, the data indicate that, in contrast to CO, the NO ligand binds to the heme iron through a "harpoon" mechanism where the heme iron out-of-plane conformation presents a negligible enthalpic barrier to NO rebinding. These observations strongly support a previous analysis (Srajer et al. J. Am. Chem. Soc. 1988, 110, 6656-6670) that primarily attributes the low-temperature stretched exponential rebinding of MbCO to a quenched distribution of heme geometries. A simple model, consistent with this prior analysis, is presented that explains a variety of MbNO rebinding experiments, including the dependence of the kinetic amplitudes on the pump photon energy.
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Affiliation(s)
- Dan Ionascu
- Dept. of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston 02115
| | - Flaviu Gruia
- Dept. of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston 02115
| | - Xiong Ye
- Dept. of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston 02115
| | - Anchi Yu
- Dept. of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston 02115
| | - Florin Rosca
- Dept. of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston 02115
| | - Chris Beck
- Dept. of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston 02115
| | - Andrey Demidov
- Dept. of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston 02115
| | | | - Paul M. Champion
- Dept. of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston 02115
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47
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Dantsker D, Roche C, Samuni U, Blouin G, Olson JS, Friedman JM. The Position 68(E11) Side Chain in Myoglobin Regulates Ligand Capture, Bond Formation with Heme Iron, and Internal Movement into the Xenon Cavities. J Biol Chem 2005; 280:38740-55. [PMID: 16155005 DOI: 10.1074/jbc.m506333200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
After photodissociation, ligand rebinding to myoglobin exhibits complex kinetic patterns associated with multiple first-order geminate recombination processes occurring within the protein and a simpler bimolecular phase representing second-order ligand rebinding from the solvent. A smooth transition from cryogenic-like to solution phase properties can be obtained by using a combination of sol-gel encapsulation, addition of glycerol as a bathing medium, and temperature tuning (-15 --> 65 degrees C). This approach was applied to a series of double mutants, myoglobin CO (H64L/V68X, where X = Ala, Val, Leu, Asn, and Phe), which were designed to examine the contributions of the position 68(E11) side chain to the appearance and disappearance of internal rebinding phases in the absence of steric and polar interactions with the distal histidine. Based on the effects of viscosity, temperature, and the stereochemistry of the E11 side chain, the three major phases, B --> A, C --> A, and D --> A, can be assigned, respectively, to ligand rebinding from the following: (i) the distal heme pocket, (ii) the xenon cavities prior to large amplitude side chain conformational relaxation, and (iii) the xenon cavities after significant conformational relaxation of the position 68(E11) side chain. The relative amplitudes of the B --> A and C --> A phases depend markedly on the size and shape of the E11 side chain, which regulates sterically both ligand return to the heme iron atom and ligand migration to the xenon cavities. The internal xenon cavities provide a transient docking site that allows side chain relaxations and the entry of water into the vacated distal pocket, which in turn slows ligand recombination markedly.
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Affiliation(s)
- David Dantsker
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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48
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Tetreau C, Lavalette D. Dominant features of protein reaction dynamics: conformational relaxation and ligand migration. Biochim Biophys Acta Gen Subj 2005; 1724:411-24. [PMID: 15919157 DOI: 10.1016/j.bbagen.2005.04.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Revised: 04/08/2005] [Accepted: 04/11/2005] [Indexed: 11/15/2022]
Abstract
Here, we review the dominant aspects of protein dynamics as revealed by studying hemoproteins using the combination of laser flash photolysis, kinetic spectroscopy and low temperature. The first breakthrough was the finding that geminate ligand rebinding with myoglobin is highly non-exponential at temperature T<200 K, providing evidence for the trapping of a large number of protein statistical substates. Another major advance was the introduction of a "model free" approach to analyze polychromatic kinetics in terms of their rate spectrum rather than to fit the data to some arbitrarily predefined kinetic scheme. Kinetic processes are identified and quantified directly from the rate spectrum without a priori assumptions. In recent years, further progresses were achieved by using xenon gas as a soft external perturbing agent that competes with ligand rebinding pathways by occupying hydrophobic protein cavities. The first part of this paper introduces several basic principles that are spread throughout a vast literature. The second part describes the main conclusions regarding conformational relaxation and ligand migration in hemoproteins obtained by combining these approaches.
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Affiliation(s)
- Catherine Tetreau
- Institut Curie-Recherche, Bâtiment 112, Centre Universitaire, 91405 ORSAY, France
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49
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Schmidt M, Nienhaus K, Pahl R, Krasselt A, Anderson S, Parak F, Nienhaus GU, Srajer V. Ligand migration pathway and protein dynamics in myoglobin: a time-resolved crystallographic study on L29W MbCO. Proc Natl Acad Sci U S A 2005; 102:11704-9. [PMID: 16085709 PMCID: PMC1187994 DOI: 10.1073/pnas.0504932102] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
By using time-resolved x-ray crystallography at room temperature, structural relaxations and ligand migration were examined in myoglobin (Mb) mutant L29W from nanoseconds to seconds after photodissociation of carbon monoxide (CO) from the heme iron by nanosecond laser pulses. The data were analyzed in terms of transient kinetics by fitting trial functions to integrated difference electron density values obtained from select structural moieties, thus allowing a quantitative description of the processes involved. The observed relaxations are linked to other investigations on protein dynamics. At the earliest times, the heme has already completely relaxed into its domed deoxy structure, and there is no photo-dissociated CO visible at the primary docking site. Initial relaxations of larger globin moieties are completed within several hundred nanoseconds. They influence the concomitant migration of photo-dissociated CO to the Xe1 site, where it appears at approximately 300 ns and leaves again at approximately 1.5 ms. The extremely long residence time in Xe1 as compared with wild-type MbCO implies that, in the latter protein, the CO exits the protein from Xe1 predominantly via the distal pocket. A well-defined deligated state is populated between approximately 2 micros and approximately 1 ms; its structure is very similar to the equilibrium deoxy structure. Between 1.5 and 20 ms, no CO is visible in the protein interior; it is either distributed among many sites within the protein or has escaped to the solvent. Finally, recombination at the heme iron occurs after >20 ms.
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Affiliation(s)
- Marius Schmidt
- Physikdepartment E17, Technische Universität München, James Franck Strasse, 85747 Garching, Germany.
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50
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Mouawad L, Maréchal JD, Perahia D. Internal cavities and ligand passageways in human hemoglobin characterized by molecular dynamics simulations. Biochim Biophys Acta Gen Subj 2005; 1724:385-93. [PMID: 15963643 DOI: 10.1016/j.bbagen.2005.05.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2005] [Revised: 05/11/2005] [Accepted: 05/12/2005] [Indexed: 11/30/2022]
Abstract
Molecular dynamics simulations of the unliganded T state of human hemoglobin showed the existence of a spontaneous, very wide cavity on the distal side of the alpha subunit. This cavity consists of three tunnels spreading from the vicinity of the iron atom (the ligand binding site) to the surface of the subunit, constituting possible passageways for the entrance of the ligand. A fourth passageway was characterized due to the trajectory of water molecules entering or leaving the heme pocket. Analogous passages were observed in the beta subunits. They all appear and disappear dynamically, although some parts of them are more persistent along the trajectories. The most persistent regions within these tunnels correspond to all the xenon docking sites of human cytoglobin and to some of those of sperm whale and horse heart myoglobins and group I truncated hemoglobins.
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Affiliation(s)
- Liliane Mouawad
- Laboratoire de Biophysique Moléculaire, Institut Curie, Université Paris-Sud, Bât. 112, 91405 Orsay Cedex, France.
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