1
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Halder R, Warshel A. Energetic and structural insights behind calcium induced conformational transition in calmodulin. Proteins 2024; 92:384-394. [PMID: 37915244 PMCID: PMC10872638 DOI: 10.1002/prot.26620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Revised: 10/01/2023] [Accepted: 10/10/2023] [Indexed: 11/03/2023]
Abstract
Calmodulin (CaM) is a key signaling protein that triggers several cellular and physiological processes inside the cell. Upon binding with calcium ion, CaM undergoes large scale conformational transition from a closed state to an open state that facilitates its interaction with various target protein and regulates their activity. This work explores the origin of the energetic and structural variation of the wild type and mutated CaM and explores the molecular origin for the structural differences between them. We first calculated the sequential calcium binding energy to CaM using the PDLD/S-LRA/β approach. This study shows a very good correlation with experimental calcium binding energies. Next we calculated the calcium binding energies to the wild type CaM and several mutated CaM systems which were reported experimentally. On the structural aspect, it has been reported experimentally that certain mutation (Q41L-K75I) in calcium bound CaM leads to complete conformational transition from an open to a closed state. By using equilibrium molecular dynamics simulation, free energy calculation and contact frequency map analysis, we have shown that the formation of a cluster of long-range hydrophobic contacts, initiated by the Q41L-K75I CaM variant is the driving force behind its closing motion. This study unravels the energetics and structural aspects behind calcium ion induced conformational changes in wild type CaM and its variant.
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Affiliation(s)
- Ritaban Halder
- Department of Chemistry, University of Southern California, Los Angeles, California, USA
| | - Arieh Warshel
- Department of Chemistry, University of Southern California, Los Angeles, California, USA
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2
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Nachliel E, Gutman M. Reaction within the coulomb-cage; science in retrospect. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184071. [PMID: 36244436 DOI: 10.1016/j.bbamem.2022.184071] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 08/01/2022] [Accepted: 09/30/2022] [Indexed: 11/06/2022]
Abstract
The Coulomb-cage is defined as the space where the electrostatic interaction between two bodies is more intensive than the thermal energy (kBT). For small molecule, the Coulomb-cage is a small sphere, extending only few water molecules towards the bulk and its radius is sensitive to the ionic strength of the solution. For charged proteins or membranal structures, the Coulomb-cage can engulf large fraction of the surface and provides a preferred pathway for ion propagation along the surface. Similarly, electrostatic potential at the inner space of a channel can form preferential trajectories passage for ions. The dynamics of ions inside the Coulomb-cage of ions was formulated by the studies of proton-anion recombination of excited photoacids. In the present article, we recount the study of intra- Coulomb-cage reaction taking place on the surface of macro-molecular bodies like micelles, membranes, proteins and intra-protein cavities. The study progressed stepwise, tracing the dynamics of a proton ejected from a photo-acid molecule located at defined sites (on membrane, inter-membrane space, active site of enzyme, inside Large Pore Channels etc.). Accumulation of experimental observations encouraged us to study of the reaction mechanism by molecular dynamics simulations of ions within the Coulomb-cage of proteins surface or inside large pores. The intra-Coulomb-cage proton transfer events follows closely the fine structure of the electrostatic field inside the cage and reflects the shape of nearby dielectric boundaries, the temporal ordering of the solvent molecules and the structural fluctuations of the charged side chains. The article sums some 40 years of research, which in retrospect clarifies the intra-Coulomb-cage reaction mechanism.
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Affiliation(s)
- E Nachliel
- Laser Laboratory for Fast Reactions, Dep. Of Biochemistry and Molecular Biology, Life Sciences, Tel Aviv University, Israel
| | - M Gutman
- Laser Laboratory for Fast Reactions, Dep. Of Biochemistry and Molecular Biology, Life Sciences, Tel Aviv University, Israel.
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3
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Yaduvanshi S, Ero R, Kumar V. The mechanism of complex formation between calmodulin and voltage gated calcium channels revealed by molecular dynamics. PLoS One 2021; 16:e0258112. [PMID: 34610038 PMCID: PMC8491939 DOI: 10.1371/journal.pone.0258112] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Accepted: 09/18/2021] [Indexed: 11/18/2022] Open
Abstract
Calmodulin, a ubiquitous eukaryotic calcium sensor responsible for the regulation of many fundamental cellular processes, is a highly flexible protein and exhibits an unusually wide range of conformations. Furthermore, CaM is known to interact with more than 300 cellular targets. Molecular dynamics (MD) simulation trajectories suggest that EF-hand loops show different magnitudes of flexibility. Therefore, the four EF-hand motifs have different affinities for Ca2+ ions, which enables CaM to function on wide range of Ca2+ ion concentrations. EF-hand loops are 2-3 times more flexible in apo CaM whereas least flexible in Ca2+/CaM-IQ motif complexes. We report a unique intermediate conformation of Ca2+/CaM while transitioning from extended to compact form. We also report the complex formation process between Ca2+/CaM and IQ CaM-binding motifs. Our results showed how IQ motif recognise its binding site on the CaM and how CaM transforms from extended to compact form upon binding to IQ motif.
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Affiliation(s)
- Shivani Yaduvanshi
- Amity Institute of Molecular Medicine and Stem Cell Research (AIMMSCR), Amity University Noida, Noida, Uttar Pradesh, India
| | - Rya Ero
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
| | - Veerendra Kumar
- Amity Institute of Molecular Medicine and Stem Cell Research (AIMMSCR), Amity University Noida, Noida, Uttar Pradesh, India
- * E-mail:
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4
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Nde J, Zhang P, Ezerski JC, Lu W, Knapp K, Wolynes PG, Cheung MS. Coarse-Grained Modeling and Molecular Dynamics Simulations of Ca 2+-Calmodulin. Front Mol Biosci 2021; 8:661322. [PMID: 34504868 PMCID: PMC8421859 DOI: 10.3389/fmolb.2021.661322] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 07/21/2021] [Indexed: 12/21/2022] Open
Abstract
Calmodulin (CaM) is a calcium-binding protein that transduces signals to downstream proteins through target binding upon calcium binding in a time-dependent manner. Understanding the target binding process that tunes CaM’s affinity for the calcium ions (Ca2+), or vice versa, may provide insight into how Ca2+-CaM selects its target binding proteins. However, modeling of Ca2+-CaM in molecular simulations is challenging because of the gross structural changes in its central linker regions while the two lobes are relatively rigid due to tight binding of the Ca2+ to the calcium-binding loops where the loop forms a pentagonal bipyramidal coordination geometry with Ca2+. This feature that underlies the reciprocal relation between Ca2+ binding and target binding of CaM, however, has yet to be considered in the structural modeling. Here, we presented a coarse-grained model based on the Associative memory, Water mediated, Structure, and Energy Model (AWSEM) protein force field, to investigate the salient features of CaM. Particularly, we optimized the force field of CaM and that of Ca2+ ions by using its coordination chemistry in the calcium-binding loops to match with experimental observations. We presented a “community model” of CaM that is capable of sampling various conformations of CaM, incorporating various calcium-binding states, and carrying the memory of binding with various targets, which sets the foundation of the reciprocal relation of target binding and Ca2+ binding in future studies.
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Affiliation(s)
- Jules Nde
- Department of Physics, University of Houston, Houston, TX, United States.,Center for Theoretical Biological Physics, Rice University, Houston, TX, United States
| | - Pengzhi Zhang
- Department of Physics, University of Houston, Houston, TX, United States
| | - Jacob C Ezerski
- Department of Physics, University of Houston, Houston, TX, United States
| | - Wei Lu
- Center for Theoretical Biological Physics, Rice University, Houston, TX, United States
| | - Kaitlin Knapp
- Center for Theoretical Biological Physics, Rice University, Houston, TX, United States
| | - Peter G Wolynes
- Center for Theoretical Biological Physics, Rice University, Houston, TX, United States
| | - Margaret S Cheung
- Department of Physics, University of Houston, Houston, TX, United States.,Center for Theoretical Biological Physics, Rice University, Houston, TX, United States
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5
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Ahlstrand E, Zukerman Schpector J, Friedman R. Computer simulations of alkali-acetate solutions: Accuracy of the forcefields in difference concentrations. J Chem Phys 2018; 147:194102. [PMID: 29166095 DOI: 10.1063/1.4985919] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
When proteins are solvated in electrolyte solutions that contain alkali ions, the ions interact mostly with carboxylates on the protein surface. Correctly accounting for alkali-carboxylate interactions is thus important for realistic simulations of proteins. Acetates are the simplest carboxylates that are amphipathic, and experimental data for alkali acetate solutions are available and can be compared with observables obtained from simulations. We carried out molecular dynamics simulations of alkali acetate solutions using polarizable and non-polarizable forcefields and examined the ion-acetate interactions. In particular, activity coefficients and association constants were studied in a range of concentrations (0.03, 0.1, and 1M). In addition, quantum-mechanics (QM) based energy decomposition analysis was performed in order to estimate the contribution of polarization, electrostatics, dispersion, and QM (non-classical) effects on the cation-acetate and cation-water interactions. Simulations of Li-acetate solutions in general overestimated the binding of Li+ and acetates. In lower concentrations, the activity coefficients of alkali-acetate solutions were too high, which is suggested to be due to the simulation protocol and not the forcefields. Energy decomposition analysis suggested that improvement of the forcefield parameters to enable accurate simulations of Li-acetate solutions can be achieved but may require the use of a polarizable forcefield. Importantly, simulations with some ion parameters could not reproduce the correct ion-oxygen distances, which calls for caution in the choice of ion parameters when protein simulations are performed in electrolyte solutions.
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Affiliation(s)
- Emma Ahlstrand
- Department of Chemistry and Biomedical Sciences, Linnæus University, 391 82 Kalmar, Sweden
| | - Julio Zukerman Schpector
- Universidade Federal de São Carlos, Departamento de Química, CP 676, 13565-905 São Carlos, SP, Brazil
| | - Ran Friedman
- Department of Chemistry and Biomedical Sciences, Linnæus University, 391 82 Kalmar, Sweden
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6
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Westerlund AM, Delemotte L. Effect of Ca2+ on the promiscuous target-protein binding of calmodulin. PLoS Comput Biol 2018; 14:e1006072. [PMID: 29614072 PMCID: PMC5898786 DOI: 10.1371/journal.pcbi.1006072] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 04/13/2018] [Accepted: 03/07/2018] [Indexed: 01/05/2023] Open
Abstract
Calmodulin (CaM) is a calcium sensing protein that regulates the function of a large number of proteins, thus playing a crucial part in many cell signaling pathways. CaM has the ability to bind more than 300 different target peptides in a Ca2+-dependent manner, mainly through the exposure of hydrophobic residues. How CaM can bind a large number of targets while retaining some selectivity is a fascinating open question. Here, we explore the mechanism of CaM selective promiscuity for selected target proteins. Analyzing enhanced sampling molecular dynamics simulations of Ca2+-bound and Ca2+-free CaM via spectral clustering has allowed us to identify distinct conformational states, characterized by interhelical angles, secondary structure determinants and the solvent exposure of specific residues. We searched for indicators of conformational selection by mapping solvent exposure of residues in these conformational states to contacts in structures of CaM/target peptide complexes. We thereby identified CaM states involved in various binding classes arranged along a depth binding gradient. Binding Ca2+ modifies the accessible hydrophobic surface of the two lobes and allows for deeper binding. Apo CaM indeed shows shallow binding involving predominantly polar and charged residues. Furthermore, binding to the C-terminal lobe of CaM appears selective and involves specific conformational states that can facilitate deep binding to target proteins, while binding to the N-terminal lobe appears to happen through a more flexible mechanism. Thus the long-ranged electrostatic interactions of the charged residues of the N-terminal lobe of CaM may initiate binding, while the short-ranged interactions of hydrophobic residues in the C-terminal lobe of CaM may account for selectivity. This work furthers our understanding of the mechanism of CaM binding and selectivity to different target proteins and paves the way towards a comprehensive model of CaM selectivity.
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Affiliation(s)
- Annie M. Westerlund
- Science for Life Laboratory, Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Lucie Delemotte
- Science for Life Laboratory, Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
- * E-mail:
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7
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Rong Z, Zhao Y, Shi E, Zhang W, Yang B. Comparative Electrochemical Study of N-, C-terminal and Integral Centrin on Adsorption and Metal-Binding Properties. ELECTROANAL 2017. [DOI: 10.1002/elan.201600698] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Zhijiang Rong
- Institute of Molecular Science, Key Laboratory of Chemical Biology of Molecular Engineering of Education Ministry; Shanxi University; Taiyuan 030006 PR China
- School of Environment and Safety; Taiyuan University of Science and Technology; Taiyuan 030024 PR China
| | - Yaqin Zhao
- Institute of Molecular Science, Key Laboratory of Chemical Biology of Molecular Engineering of Education Ministry; Shanxi University; Taiyuan 030006 PR China
| | - Enxian Shi
- Institute of Molecular Science, Key Laboratory of Chemical Biology of Molecular Engineering of Education Ministry; Shanxi University; Taiyuan 030006 PR China
- College of Pharmacy; Shanxi Medical University; Taiyuan 030006 PR China
| | - Wenlong Zhang
- Institute of Molecular Science, Key Laboratory of Chemical Biology of Molecular Engineering of Education Ministry; Shanxi University; Taiyuan 030006 PR China
| | - Binsheng Yang
- Institute of Molecular Science, Key Laboratory of Chemical Biology of Molecular Engineering of Education Ministry; Shanxi University; Taiyuan 030006 PR China
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8
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Feng M, Bell DR, Luo J, Zhou R. Impact of graphyne on structural and dynamical properties of calmodulin. Phys Chem Chem Phys 2017; 19:10187-10195. [PMID: 28374026 DOI: 10.1039/c7cp00720e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Carbon-based nanomaterials such as graphyne, graphene, and carbon nanotubes have attracted considerable attention for their applications, but questions remain regarding their biosafety through potential adverse interactions with important biomolecules.
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Affiliation(s)
- Mei Feng
- Department of Physics
- Institute of Quantitative Biology
- Zhejiang University
- Hangzhou
- China
| | - David R. Bell
- Computational Biological Center
- IBM Thomas J. Watson Research Center
- Yorktown Heights
- USA
| | - Judong Luo
- Department of Oncology
- The Affiliated Hospital of Nanjing Medical University
- Changzhou No. 2 People's Hospital
- Changzhou
- China
| | - Ruhong Zhou
- Department of Physics
- Institute of Quantitative Biology
- Zhejiang University
- Hangzhou
- China
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9
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Origin and prediction of free-solution interaction studies performed label-free. Proc Natl Acad Sci U S A 2016; 113:E1595-604. [PMID: 26960999 DOI: 10.1073/pnas.1515706113] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Interaction/reaction assays have led to significant scientific discoveries in the biochemical, medical, and chemical disciplines. Several fundamental driving forces form the basis of intermolecular and intramolecular interactions in chemical and biochemical systems (London dispersion, hydrogen bonding, hydrophobic, and electrostatic), and in the past three decades the sophistication and power of techniques to interrogate these processes has developed at an unprecedented rate. In particular, label-free methods have flourished, such as NMR, mass spectrometry (MS), surface plasmon resonance (SPR), biolayer interferometry (BLI), and backscattering interferometry (BSI), which can facilitate assays without altering the participating components. The shortcoming of most refractive index (RI)-based label-free methods such as BLI and SPR is the requirement to tether one of the interaction entities to a sensor surface. This is not the case for BSI. Here, our hypothesis is that the signal origin for free-solution, label-free determinations can be attributed to conformation and hydration-induced changes in the solution RI. We propose a model for the free-solution response function (FreeSRF) and show that, when quality bound and unbound structural data are available, FreeSRF correlates well with the experiment (R(2)> 0.99, Spearman rank correlation coefficients >0.9) and the model is predictive within ∼15% of the experimental binding signal. It is also demonstrated that a simple mass-weighted dη/dC response function is the incorrect equation to determine that the change in RI is produced by binding or folding event in free solution.
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10
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Sampath B, Sankaranarayanan K. Glu106 targeted inhibitors of ORAI1 as potential Ca 2+ release-activated Ca 2+ (CRAC) channel blockers - molecular modeling and docking studies. J Recept Signal Transduct Res 2016; 36:572-585. [PMID: 26895524 DOI: 10.3109/10799893.2016.1141956] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Calcium release-activated calcium modulator 1(ORAI1) is an integral component of the calcium release-activated calcium channel (CRAC) channel complex and plays a central role in regulating Ca2 + concentrations in T-lymphocytes. It is critical for many physiological processes, including cell-proliferation, cytokine production and activation of the immune system. Loss of ORAI1 function is linked with rheumatoid arthritis (RA) and hence pharmacological blockers of ORAI1 could be potential therapeutic agents for the treatment of RA. In this study, we have used a high-throughput screening approach to inhibit the binding of Ca2+ toward ORAI1 and the interactions are verified through induced fit docking. The results hint that these compounds act by possibly binding with, and thereby blocking Ca2+-binding with ORAI1 (E106). The molecular dynamics (MD) simulations shows strong support toward the hit compounds by showing the ligand potency throughout the simulation timescale of 30 ns. We have thus identified a novel class of highly stable, potential lead compounds that directly bind with the selectivity filter region E106 and block Ca2+ binding on ORAI1. This resulting alteration in the pore geometry of ORAI1 due to the strong blocking mechanism of lead compounds will greatly diminish its function and the downstream activities that result from the same including decreased production of cytokines in autoimmune disorders. This study may lay the foundation for finding novel lead compounds for clinical trials that could positively modulate the course of autoimmune disorders with ORAI1 as its specific target.
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Affiliation(s)
- Bhuvaneshwari Sampath
- a Ion Channel Biology Laboratory, AU-KBC Research Centre, Madras Institute of Technology, Anna University , Chennai , Tamil Nadu , India
| | - Kavitha Sankaranarayanan
- a Ion Channel Biology Laboratory, AU-KBC Research Centre, Madras Institute of Technology, Anna University , Chennai , Tamil Nadu , India
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11
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Yu Y, Wang J, Shao Q, Shi J, Zhu W. Increasing the sampling efficiency of protein conformational transition using velocity-scaling optimized hybrid explicit/implicit solvent REMD simulation. J Chem Phys 2015; 142:125105. [PMID: 25833612 DOI: 10.1063/1.4916118] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The application of temperature replica exchange molecular dynamics (REMD) simulation on protein motion is limited by its huge requirement of computational resource, particularly when explicit solvent model is implemented. In the previous study, we developed a velocity-scaling optimized hybrid explicit/implicit solvent REMD method with the hope to reduce the temperature (replica) number on the premise of maintaining high sampling efficiency. In this study, we utilized this method to characterize and energetically identify the conformational transition pathway of a protein model, the N-terminal domain of calmodulin. In comparison to the standard explicit solvent REMD simulation, the hybrid REMD is much less computationally expensive but, meanwhile, gives accurate evaluation of the structural and thermodynamic properties of the conformational transition which are in well agreement with the standard REMD simulation. Therefore, the hybrid REMD could highly increase the computational efficiency and thus expand the application of REMD simulation to larger-size protein systems.
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Affiliation(s)
- Yuqi Yu
- ACS Key Laboratory of Receptor Research, Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Jinan Wang
- ACS Key Laboratory of Receptor Research, Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Qiang Shao
- ACS Key Laboratory of Receptor Research, Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Jiye Shi
- UCB Pharma, 216 Bath Road, Slough SL1 4EN, United Kingdom
| | - Weiliang Zhu
- ACS Key Laboratory of Receptor Research, Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
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12
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Vaidehi N, Jain A. Internal coordinate molecular dynamics: a foundation for multiscale dynamics. J Phys Chem B 2015; 119:1233-42. [PMID: 25517406 PMCID: PMC4315417 DOI: 10.1021/jp509136y] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Internal coordinates such as bond
lengths, bond angles, and torsion
angles (BAT) are natural coordinates for describing a bonded molecular
system. However, the molecular dynamics (MD) simulation methods that
are widely used for proteins, DNA, and polymers are based on Cartesian
coordinates owing to the mathematical simplicity of the equations
of motion. However, constraints are often needed with Cartesian MD
simulations to enhance the conformational sampling. This makes the
equations of motion in the Cartesian coordinates differential-algebraic,
which adversely impacts the complexity and the robustness of the simulations.
On the other hand, constraints can be easily placed in BAT coordinates
by removing the degrees of freedom that need to be constrained. Thus,
the internal coordinate MD (ICMD) offers an attractive alternative
to Cartesian coordinate MD for developing multiscale MD method. The
torsional MD method is a special adaptation of the ICMD method, where
all the bond lengths and bond angles are kept rigid. The advantages
of ICMD simulation methods are the longer time step size afforded
by freezing high frequency degrees of freedom and performing a conformational
search in the more important low frequency torsional degrees of freedom.
However, the advancements in the ICMD simulations have been slow and
stifled by long-standing mathematical bottlenecks. In this review,
we summarize the recent mathematical advancements we have made based
on spatial operator algebra, in developing a robust long time scale
ICMD simulation toolkit useful for various applications. We also present
the applications of ICMD simulations to study conformational changes
in proteins and protein structure refinement. We review the advantages
of the ICMD simulations over the Cartesian simulations when used with
enhanced sampling methods and project the future use of ICMD simulations
in protein dynamics.
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Affiliation(s)
- Nagarajan Vaidehi
- Department of Immunology, Beckman Research Institute of the City of Hope , Duarte, California 91010, United States
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13
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Effect of Calcium Ion Removal, Ionic Strength, and Temperature on the Conformation Change in Calmodulin Protein at Physiological pH. JOURNAL OF BIOPHYSICS 2014; 2014:329703. [PMID: 25548559 PMCID: PMC4274857 DOI: 10.1155/2014/329703] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Revised: 11/11/2014] [Accepted: 11/13/2014] [Indexed: 11/24/2022]
Abstract
The response of the calmodulin (CaM) protein as a function of calcium ion removal, ionic strength, and temperature at physiological pH condition was investigated using classical molecular dynamics simulations. Changing the ionic strength and temperature came out to be two of the possible routes for observing a conformation change in the protein. This behavior is similar to the conformation change observed in our previous study where a change in the pH was observed to trigger a conformation change in this protein. In the present study, as the calcium ions are removed from the protein, the protein is observed to acquire more flexibility. This flexibility is observed to be more prominent at a higher ionic strength. At a lower ionic strength of 150 mM with all the four calcium ions intact, the N- and C-lobes are observed to come close to a distance of 30 Å starting from an initial separation distance of 48 Å. This conformation change is observed to take place around 50 ns in a simulation of 100 ns. As a second parameter, temperature is observed to play a key role in the conformation change of the protein. With an increase in the temperature, the protein is observed to acquire a more compact form with the formation of different salt bridges between the residues of the N- and the C-lobes. The salt bridge formation leads to an overall lowering of the energy of the protein thus favoring the bending of the two lobes towards each other. The improper and dihedral terms show a significant shift thus leading to a more compact form on increasing the temperature. Another set of simulations is also performed at an increased temperature of 500 K to verify the reproducibility of the results. Thus a set of three possible alterations in the environmental conditions of the protein CaM are studied, with two of them giving rise to a conformation change and one adding flexibility to the protein.
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14
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Kohagen M, Lepšík M, Jungwirth P. Calcium Binding to Calmodulin by Molecular Dynamics with Effective Polarization. J Phys Chem Lett 2014; 5:3964-3969. [PMID: 26276478 DOI: 10.1021/jz502099g] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Calcium represents a key biological signaling ion with the EF-hand loops being its most prevalent binding motif in proteins. We show using molecular dynamics simulations with umbrella sampling that including electronic polarization effects via ionic charge rescaling dramatically improves agreements with experiment in terms of the strength of calcium binding and structures of the calmodulin binding sites. The present study thus opens way to accurate calculations of interactions of calcium and other computationally difficult high-charge-density ions in biological contexts.
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Affiliation(s)
- Miriam Kohagen
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nam. 2, 16610 Prague 6, Czech Republic
| | - Martin Lepšík
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nam. 2, 16610 Prague 6, Czech Republic
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nam. 2, 16610 Prague 6, Czech Republic
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15
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Gao J, Wang L, Kang SG, Zhao L, Ji M, Chen C, Zhao Y, Zhou R, Li J. Size-dependent impact of CNTs on dynamic properties of calmodulin. NANOSCALE 2014; 6:12828-37. [PMID: 25225777 DOI: 10.1039/c4nr01623h] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
There are growing concerns about the biosafety of nanomaterials such as carbon nanotubes (CNTs) as their applications become more widespread. We report here a theoretical and experimental study of the binding of various sizes of CNTs [CNT (4,4), (5,5), (6,6) and (7,7)] to calmodulin (CaM) protein and, in particular, their impact on the Ca(2+)-dependent dynamic properties of CaM. Our simulations show that all the CNTs can plug into the hydrophobic binding pocket of Ca(2+)-bound CaM with binding affinities comparable with the native substrate M13 peptide. Even though CNT (4,4) shows a similar behavior to the M13 peptide in its dissociation from Ca(2+)-free CaM, wider CNTs still bind firmly to CaM, indicating a potential failure of Ca(2+) regulation. Such a size-dependent impact of CNTs on the dynamic properties of CaM is a result of the excessively strong hydrophobic interactions between the wider CNTs and CaM. These simulation results were confirmed by circular dichroism spectroscopy, which showed that the secondary structures of CaM become insensitive to Ca(2+) concentrations after the addition of CNTs. Our findings indicate that the cytotoxicity of nanoparticles to proteins arises not only from the inhibition of static protein structures (binding pockets), but also from impacts on their dynamic properties.
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Affiliation(s)
- Jian Gao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials & Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences (CAS), Beijing 100049, China.
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16
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Designing molecular dynamics simulations to shift populations of the conformational states of calmodulin. PLoS Comput Biol 2013; 9:e1003366. [PMID: 24339763 PMCID: PMC3854495 DOI: 10.1371/journal.pcbi.1003366] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Accepted: 10/11/2013] [Indexed: 11/19/2022] Open
Abstract
We elucidate the mechanisms that lead to population shifts in the conformational states of calcium-loaded calmodulin (Ca2+-CaM). We design extensive molecular dynamics simulations to classify the effects that are responsible for adopting occupied conformations available in the ensemble of NMR structures. Electrostatic interactions amongst the different regions of the protein and with its vicinal water are herein mediated by lowering the ionic strength or the pH. Amino acid E31, which is one of the few charged residues whose ionization state is highly sensitive to pH differences in the physiological range, proves to be distinctive in its control of population shifts. E31A mutation at low ionic strength results in a distinct change from an extended to a compact Ca2+-CaM conformation within tens of nanoseconds, that otherwise occur on the time scales of microseconds. The kinked linker found in this particular compact form is observed in many of the target-bound forms of Ca2+-CaM, increasing the binding affinity. This mutation is unique in controlling C-lobe dynamics by affecting the fluctuations between the EF-hand motif helices. We also monitor the effect of the ionic strength on the conformational multiplicity of Ca2+-CaM. By lowering the ionic strength, the tendency of nonspecific anions in water to accumulate near the protein surface increases, especially in the vicinity of the linker. The change in the distribution of ions in the vicinal layer of water allows N- and C- lobes to span a wide variety of relative orientations that are otherwise not observed at physiological ionic strength. E31 protonation restores the conformations associated with physiological environmental conditions even at low ionic strength. Calmodulin (CaM) is involved in calcium signaling pathways in eukaryotic cells as an intracellular Ca2+ receptor. Exploiting pH differences in the cell, CaM performs a variety of functions by conveniently adopting different conformational states. We aim to reveal pH and ionic strength (IS) dependent shifts in the populations of conformational substates by modulating electrostatic interactions amongst the different regions of the protein and with its vicinal water. For this purpose, we design extensive molecular dynamics simulations to classify the effects that are responsible for adopting different conformations exhibited in the ensemble of NMR structures reported. Lowering the IS or pH, CaM experiences higher inter-lobe orientational flexibility caused by extreme change in the non-specific ion distribution in the vicinal solvent. Amongst the titratable groups sensitive to pH variations, E31 is unique in that its protonation has the same effect on the vicinal layer as increasing the IS. Furthermore, E31A mutation causes a large, reversible conformational change compatible with NMR ensemble structures populating the linker-kinked conformations. The mutation in the N lobe, at a significant distance, both modulates the electrostatic interactions in the central linker and alters the EF-hand helix orientations in the C lobe.
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17
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Gangupomu VK, Wagner JR, Park IH, Jain A, Vaidehi N. Mapping conformational dynamics of proteins using torsional dynamics simulations. Biophys J 2013; 104:1999-2008. [PMID: 23663843 DOI: 10.1016/j.bpj.2013.01.050] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 01/07/2013] [Accepted: 01/17/2013] [Indexed: 10/26/2022] Open
Abstract
All-atom molecular dynamics simulations are widely used to study the flexibility of protein conformations. However, enhanced sampling techniques are required for simulating protein dynamics that occur on the millisecond timescale. In this work, we show that torsional molecular dynamics simulations enhance protein conformational sampling by performing conformational search in the low-frequency torsional degrees of freedom. In this article, we use our recently developed torsional-dynamics method called Generalized Newton-Euler Inverse Mass Operator (GNEIMO) to study the conformational dynamics of four proteins. We investigate the use of the GNEIMO method in simulations of the conformationally flexible proteins fasciculin and calmodulin, as well as the less flexible crambin and bovine pancreatic trypsin inhibitor. For the latter two proteins, the GNEIMO simulations with an implicit-solvent model reproduced the average protein structural fluctuations and sample conformations similar to those from Cartesian simulations with explicit solvent. The application of GNEIMO with replica exchange to the study of fasciculin conformational dynamics produced sampling of two of this protein's experimentally established conformational substates. Conformational transition of calmodulin from the Ca(2+)-bound to the Ca(2+)-free conformation occurred readily with GNEIMO simulations. Moreover, the GNEIMO method generated an ensemble of conformations that satisfy about half of both short- and long-range interresidue distances obtained from NMR structures of holo to apo transitions in calmodulin. Although unconstrained all-atom Cartesian simulations have failed to sample transitions between the substates of fasciculin and calmodulin, GNEIMO simulations show the transitions in both systems. The relatively short simulation times required to capture these long-timescale conformational dynamics indicate that GNEIMO is a promising molecular-dynamics technique for studying domain motion in proteins.
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Affiliation(s)
- Vamshi K Gangupomu
- Division of Immunology, Beckman Research Institute of the City of Hope, Duarte, California, USA
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18
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Molloy K, Shehu A. Elucidating the ensemble of functionally-relevant transitions in protein systems with a robotics-inspired method. BMC STRUCTURAL BIOLOGY 2013; 13 Suppl 1:S8. [PMID: 24565158 PMCID: PMC3952944 DOI: 10.1186/1472-6807-13-s1-s8] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Background Many proteins tune their biological function by transitioning between different functional states, effectively acting as dynamic molecular machines. Detailed structural characterization of transition trajectories is central to understanding the relationship between protein dynamics and function. Computational approaches that build on the Molecular Dynamics framework are in principle able to model transition trajectories at great detail but also at considerable computational cost. Methods that delay consideration of dynamics and focus instead on elucidating energetically-credible conformational paths connecting two functionally-relevant structures provide a complementary approach. Effective sampling-based path planning methods originating in robotics have been recently proposed to produce conformational paths. These methods largely model short peptides or address large proteins by simplifying conformational space. Methods We propose a robotics-inspired method that connects two given structures of a protein by sampling conformational paths. The method focuses on small- to medium-size proteins, efficiently modeling structural deformations through the use of the molecular fragment replacement technique. In particular, the method grows a tree in conformational space rooted at the start structure, steering the tree to a goal region defined around the goal structure. We investigate various bias schemes over a progress coordinate for balance between coverage of conformational space and progress towards the goal. A geometric projection layer promotes path diversity. A reactive temperature scheme allows sampling of rare paths that cross energy barriers. Results and conclusions Experiments are conducted on small- to medium-size proteins of length up to 214 amino acids and with multiple known functionally-relevant states, some of which are more than 13Å apart of each-other. Analysis reveals that the method effectively obtains conformational paths connecting structural states that are significantly different. A detailed analysis on the depth and breadth of the tree suggests that a soft global bias over the progress coordinate enhances sampling and results in higher path diversity. The explicit geometric projection layer that biases the exploration away from over-sampled regions further increases coverage, often improving proximity to the goal by forcing the exploration to find new paths. The reactive temperature scheme is shown effective in increasing path diversity, particularly in difficult structural transitions with known high-energy barriers.
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19
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Genchev GZ, Kobayashi T, Lu H. Calcium induced regulation of skeletal troponin--computational insights from molecular dynamics simulations. PLoS One 2013; 8:e58313. [PMID: 23554884 PMCID: PMC3598806 DOI: 10.1371/journal.pone.0058313] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 02/01/2013] [Indexed: 01/11/2023] Open
Abstract
The interaction between calcium and the regulatory site(s) of striated muscle regulatory protein troponin switches on and off muscle contraction. In skeletal troponin binding of calcium to sites I and II of the TnC subunit results in a set of structural changes in the troponin complex, displaces tropomyosin along the actin filament and allows myosin-actin interaction to produce mechanical force. In this study, we used molecular dynamics simulations to characterize the calcium dependent dynamics of the fast skeletal troponin molecule and its TnC subunit in the calcium saturated and depleted states. We focused on the N-lobe and on describing the atomic level events that take place subsequent to removal of the calcium ion from the regulatory sites I and II. A main structural event - a closure of the A/B helix hydrophobic pocket results from the integrated effect of the following conformational changes: the breakage of H-bond interactions between the backbone nitrogen atoms of the residues at positions 2, 9 and sidechain oxygen atoms of the residue at position 12 (N2-OE12/N9-OE12) in sites I and II; expansion of sites I and II and increased site II N-terminal end-segment flexibility; strengthening of the β-sheet scaffold; and the subsequent re-packing of the N-lobe hydrophobic residues. Additionally, the calcium release allows the N-lobe to rotate relative to the rest of the Tn molecule. Based on the findings presented herein we propose a novel model of skeletal thin filament regulation.
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Affiliation(s)
- Georgi Z. Genchev
- Bioinformatics Program, Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Tomoyoshi Kobayashi
- Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois, United States of America
- * E-mail: (HL); (TK)
| | - Hui Lu
- Bioinformatics Program, Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States of America
- Shanghai Institute of Medical Genetics, Children’s Hospital of Shanghai, Shanghai, China
- Key Lab of Embryo Molecular Biology, Ministry of Health, Shanghai, China
- Shanghai Lab of Embryo and Reproduction Engineering, Shanghai, China
- * E-mail: (HL); (TK)
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20
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Computational investigation of the key factors affecting the second stage activation mechanisms of domain II m-calpain. J Mol Model 2013; 19:779-92. [DOI: 10.1007/s00894-012-1604-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 09/21/2012] [Indexed: 10/27/2022]
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21
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Smith DMA, Straatsma TP, Squier TC. Retention of conformational entropy upon calmodulin binding to target peptides is driven by transient salt bridges. Biophys J 2012; 103:1576-84. [PMID: 23062350 DOI: 10.1016/j.bpj.2012.08.037] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 08/06/2012] [Accepted: 08/17/2012] [Indexed: 10/27/2022] Open
Abstract
Calmodulin (CaM) is a highly flexible calcium-binding protein that mediates signal transduction through an ability to differentially bind to highly variable binding sequences in target proteins. To identify how binding affects CaM motions, and its relationship to conformational entropy and target peptide sequence, we have employed fully atomistic, explicit solvent molecular dynamics simulations of unbound CaM and CaM bound to five different target peptides. The calculated CaM conformational binding entropies correlate with experimentally derived conformational entropies with a correlation coefficient R(2) of 0.95. Selected side-chain interactions with target peptides restrain interhelical loop motions, acting to tune the conformational entropy of the bound complex via widely distributed CaM motions. In the complex with the most conformational entropy retention (CaM in complex with the neuronal nitric oxide synthase binding sequence), Lys-148 at the C-terminus of CaM forms transient salt bridges alternating between Glu side chains in the N-domain, the central linker, and the binding target. Additional analyses of CaM structures, fluctuations, and CaM-target interactions illuminate the interplay between electrostatic, side chain, and backbone properties in the ability of CaM to recognize and discriminate against targets by tuning its conformational entropy, and suggest a need to consider conformational dynamics in optimizing binding affinities.
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22
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Negi S, Aykut AO, Atilgan AR, Atilgan C. Calmodulin readily switches conformation upon protonating high pKa acidic residues. J Phys Chem B 2012; 116:7145-53. [PMID: 22624501 DOI: 10.1021/jp3032995] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
We investigate protonation as a possible route for triggering conformational change in proteins by focusing on the calmodulin (CaM) example. Two hundred nanosecond molecular dynamics (MD) simulations are performed on both the extended and compact forms of calcium loaded CaM. The stability of both structures is confirmed under prevailing conditions. Protonation of nine acidic residues with upshifted pK(a) values leads to a large conformational change in less than 100 ns. The structure attained is consistent with fluorescence resonance energy transfer experimental results as well as structures from an ensemble compatible with NMR data. Analysis of the MD trajectories summing up to one microsecond implies that the key events leading to the completion of the conformational change begins with an initial formation of a salt bridge between the N-lobe and the linker, followed by the bending of the C-lobe and the organization of a stabilizing hydrophobic patch between the lobes. We find that CaM utilizes its Ca(2+) ions to harden/soften different regions so as to achieve various conformations. Thus, barrier crossing between extended and compact forms of CaM which is normally a rare event due to the repulsive electrostatic interactions between the two lobes is facilitated by protonation of high pK(a) residues. The results delineate how pH changes might be utilized in the cell to achieve different conformation-related functions.
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Affiliation(s)
- Sunita Negi
- Sabanci University, Faculty of Engineering & Natural Sciences, Tuzla, 34956 Istanbul, Turkey
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23
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Coan KED, Swann MJ, Ottl J. Measurement and Differentiation of Ligand-Induced Calmodulin Conformations by Dual Polarization Interferometry. Anal Chem 2012; 84:1586-91. [DOI: 10.1021/ac202844e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kristin E. D. Coan
- Novartis Institutes for BioMedical
Research Basel, CPC/LFP/Label-free Technologies, Novartis Pharma AG, Basel, Switzerland
| | - Marcus J. Swann
- Farfield Group Ltd., West Wing 7, Voyager, Chicago Avenue, Manchester
Airport, Manchester, M90 3DQ, United Kingdom
| | - Johannes Ottl
- Novartis Institutes for BioMedical
Research Basel, CPC/LFP/Label-free Technologies, Novartis Pharma AG, Basel, Switzerland
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24
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Selwa E, Laine E, Malliavin TE. Differential role of calmodulin and calcium ions in the stabilization of the catalytic domain of adenyl cyclase CyaA from Bordetella pertussis. Proteins 2012; 80:1028-40. [DOI: 10.1002/prot.24005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2011] [Revised: 11/04/2011] [Accepted: 11/14/2011] [Indexed: 11/10/2022]
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25
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Atilgan AR, Aykut AO, Atilgan C. Subtle pH differences trigger single residue motions for moderating conformations of calmodulin. J Chem Phys 2011; 135:155102. [DOI: 10.1063/1.3651807] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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26
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The dynamics of Ca2+ ions within the solvation shell of calbindin D9k. PLoS One 2011; 6:e14718. [PMID: 21364983 PMCID: PMC3043054 DOI: 10.1371/journal.pone.0014718] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 01/28/2011] [Indexed: 11/25/2022] Open
Abstract
The encounter of a Ca2+ ion with a protein and its subsequent
binding to specific binding sites is an intricate process that cannot be fully
elucidated from experimental observations. We have applied Molecular Dynamics to
study this process with atomistic details, using Calbindin D9k (CaB) as a model
protein. The simulations show that in most of the time the Ca2+
ion spends within the Debye radius of CaB, it is being detained at the 1st and
2nd solvation shells. While being detained near the protein, the diffusion
coefficient of the ion is significantly reduced. However, due to the relatively
long period of detainment, the ion can scan an appreciable surface of the
protein. The enhanced propagation of the ion on the surface has a functional
role: significantly increasing the ability of the ion to scan the protein's
surface before being dispersed to the bulk. The contribution of this mechanism
to Ca2+ binding becomes significant at low ion concentrations,
where the intervals between successive encounters with the protein are getting
longer. The efficiency of the surface diffusion is affected by the distribution
of charges on the protein's surface. Comparison of the Ca2+
binding dynamics in CaB and its E60D mutant reveals that in the wild type (WT)
protein the carboxylate of E60 function as a preferred landing-site for the
Ca2+ arriving from the bulk, followed by delivering it to
the final binding site. Replacement of the glutamate by aspartate significantly
reduced the ability to transfer Ca2+ ions from D60 to the final
binding site, explaining the observed decrement in the affinity of the mutated
protein to Ca2+.
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27
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Wienken CJ, Baaske P, Rothbauer U, Braun D, Duhr S. Protein-binding assays in biological liquids using microscale thermophoresis. Nat Commun 2010; 1:100. [PMID: 20981028 DOI: 10.1038/ncomms1093] [Citation(s) in RCA: 805] [Impact Index Per Article: 57.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Accepted: 09/20/2010] [Indexed: 12/20/2022] Open
Abstract
Protein interactions inside the human body are expected to differ from the situation in vitro. This is crucial when investigating protein functions or developing new drugs. In this study, we present a sample-efficient, free-solution method, termed microscale thermophoresis, that is capable of analysing interactions of proteins or small molecules in biological liquids such as blood serum or cell lysate. The technique is based on the thermophoresis of molecules, which provides information about molecule size, charge and hydration shell. We validated the method using immunologically relevant systems including human interferon gamma and the interaction of calmodulin with calcium. The affinity of the small-molecule inhibitor quercetin to its kinase PKA was determined in buffer and human serum, revealing a 400-fold reduced affinity in serum. This information about the influence of the biological matrix may allow to make more reliable conclusions on protein functionality, and may facilitate more efficient drug development.
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Affiliation(s)
- Christoph J Wienken
- Department of Physics and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Amalienstrasse 54, Munich 80799, Germany
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28
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Metal binding discrimination of the calmodulin Q41C/K75C mutant on Ca2+ and La3+. Sci China Chem 2010. [DOI: 10.1007/s11426-010-0059-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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29
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Juranic N, Atanasova E, Filoteo AG, Macura S, Prendergast FG, Penniston JT, Strehler EE. Calmodulin wraps around its binding domain in the plasma membrane Ca2+ pump anchored by a novel 18-1 motif. J Biol Chem 2009; 285:4015-4024. [PMID: 19996092 DOI: 10.1074/jbc.m109.060491] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Using solution NMR spectroscopy, we obtained the structure of Ca(2+)-calmodulin (holoCaM) in complex with peptide C28 from the binding domain of the plasma membrane Ca(2+)-ATPase (PMCA) pump isoform 4b. This provides the first atomic resolution insight into the binding mode of holoCaM to the full-length binding domain of PMCA. Structural comparison of the previously determined holoCaM.C20 complex with this holoCaM.C28 complex supports the idea that the initial binding step is represented by (holoCaM.C20) and the final bound complex by (holoCaM.C28). This affirms the existing multi-step kinetic model of PMCA4b activation by CaM. The complex exhibits a new binding motif in which holoCaM is wrapped around helical C28 peptide using two anchoring residues from the peptide at relative positions 18 and 1. The anchors correspond to Phe-1110 and Trp-1093, respectively, in full-length PMCA4b, and the peptide and CaM are oriented in an anti-parallel manner. This is a greater sequence distance between anchors than in any of the known holoCaM complexes with a helical peptide. Analysis of the geometry of holoCaM-peptide binding for the cases where the target peptide adopts an alpha(D)-helix with its anchors buried in the main hydrophobic pockets of the two CaM lobes establishes that only relative sequential positions of 10, 14, 17, and 18 are allowed for the second anchor.
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Affiliation(s)
- Nenad Juranic
- From the Departments of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905.
| | - Elena Atanasova
- From the Departments of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Adelaida G Filoteo
- From the Departments of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Slobodan Macura
- From the Departments of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Franklyn G Prendergast
- From the Departments of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905; Departments of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, Minnesota 55905 and
| | | | - Emanuel E Strehler
- From the Departments of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
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30
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Shehu A, Kavraki LE, Clementi C. Multiscale characterization of protein conformational ensembles. Proteins 2009; 76:837-51. [PMID: 19280604 DOI: 10.1002/prot.22390] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We propose a multiscale exploration method to characterize the conformational space populated by a protein at equilibrium. The method efficiently obtains a large set of equilibrium conformations in two stages: first exploring the entire space at a coarse-grained level of detail, then narrowing a refined exploration to selected low-energy regions. The coarse-grained exploration periodically adds all-atom detail to selected conformations to ensure that the search leads to regions which maintain low energies in all-atom detail. The second stage reconstructs selected low-energy coarse-grained conformations in all-atom detail. A low-dimensional energy landscape associated with all-atom conformations allows focusing the exploration to energy minima and their conformational ensembles. The lowest energy ensembles are enriched with additional all-atom conformations through further multiscale exploration. The lowest energy ensembles obtained from the application of the method to three different proteins correctly capture the known functional states of the considered systems.
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Affiliation(s)
- Amarda Shehu
- Department of Computer Science, Rice University, Houston, Texas 77005, USA
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31
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Li J, Jia Z, Zhou W, Wei Q. Calcineurin regulatory subunit B is a unique calcium sensor that regulates calcineurin in both calcium-dependent and calcium-independent manner. Proteins 2009; 77:612-23. [DOI: 10.1002/prot.22474] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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32
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Laine E, Yoneda JD, Blondel A, Malliavin TE. The conformational plasticity of calmodulin upon calcium complexation gives a model of its interaction with the oedema factor of Bacillus anthracis. Proteins 2008; 71:1813-29. [DOI: 10.1002/prot.21862] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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33
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Project E, Nachliel E, Gutman M. Parameterization of Ca+2–protein interactions for molecular dynamics simulations. J Comput Chem 2008; 29:1163-9. [PMID: 18074346 DOI: 10.1002/jcc.20876] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Elad Project
- Laser Laboratory for Fast Reactions in Biology, Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel 69978
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34
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Bornhop DJ, Latham JC, Kussrow A, Markov DA, Jones RD, Sørensen HS. Free-Solution, Label-Free Molecular Interactions Studied by Back-Scattering Interferometry. Science 2007; 317:1732-6. [PMID: 17885132 DOI: 10.1126/science.1146559] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Free-solution, label-free molecular interactions were investigated with back-scattering interferometry in a simple optical train composed of a helium-neon laser, a microfluidic channel, and a position sensor. Molecular binding interactions between proteins, ions and protein, and small molecules and protein, were determined with high dynamic range dissociation constants (Kd spanning six decades) and unmatched sensitivity (picomolar Kd's and detection limits of 10,000s of molecules). With this technique, equilibrium dissociation constants were quantified for protein A and immunoglobulin G, interleukin-2 with its monoclonal antibody, and calmodulin with calcium ion Ca2+, a small molecule inhibitor, the protein calcineurin, and the M13 peptide. The high sensitivity of back-scattering interferometry and small volumes of microfluidics allowed the entire calmodulin assay to be performed with 200 picomoles of solute.
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Affiliation(s)
- Darryl J Bornhop
- Department of Chemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt University, VU Station B 351822, Nashville, TN 37235-1822, USA.
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35
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Ganoth A, Friedman R, Nachliel E, Gutman M. A molecular dynamics study and free energy analysis of complexes between the Mlc1p protein and two IQ motif peptides. Biophys J 2006; 91:2436-50. [PMID: 16844751 PMCID: PMC1562369 DOI: 10.1529/biophysj.106.085399] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Mlc1p protein from the budding yeast Saccharomyces cerevisiae is a Calmodulin-like protein, which interacts with IQ-motif peptides located at the yeast's myosin neck. In this study, we report a molecular dynamics study of the Mlc1p-IQ2 protein-peptide complex, starting with its crystal structure, and investigate its dynamics in an aqueous solution. The results are compared with those obtained by a previous study, where we followed the solution structure of the Mlc1p-IQ4 protein-peptide complex by molecular dynamics simulations. After the simulations, we performed an interaction free-energy analysis using the molecular mechanics Poisson-Boltzmann surface area approach. Based on the dynamics of the Mlc1p-IQ protein-peptide complexes, the structure of the light-chain-binding domain of myosin V from the yeast S. cerevisiae is discussed.
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Affiliation(s)
- Assaf Ganoth
- Laser Laboratory for Fast Reactions in Biology, Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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