1
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Symonds K, Teresinski HJ, Hau B, Dwivedi V, Belausov E, Bar-Sinai S, Tominaga M, Haraguchi T, Sadot E, Ito K, Snedden WA. Functional characterization of calmodulin-like proteins, CML13 and CML14, as novel light chains of Arabidopsis class VIII myosins. JOURNAL OF EXPERIMENTAL BOTANY 2024; 75:2313-2329. [PMID: 38280207 PMCID: PMC11272076 DOI: 10.1093/jxb/erae031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 01/24/2024] [Indexed: 01/29/2024]
Abstract
Myosins are important motor proteins that associate with the actin cytoskeleton. Structurally, myosins function as heteromeric complexes where smaller light chains, such as calmodulin (CaM), bind to isoleucine-glutamine (IQ) domains in the neck region to facilitate mechano-enzymatic activity. We recently identified Arabidopsis CaM-like (CML) proteins CML13 and CML14 as interactors of proteins containing multiple IQ domains, including a myosin VIII. Here, we demonstrate that CaM, CML13, and CML14 bind the neck region of all four Arabidopsis myosin VIII isoforms. Among CMLs tested for binding to myosins VIIIs, CaM, CML13, and CML14 gave the strongest signals using in planta split-luciferase protein interaction assays. In vitro, recombinant CaM, CML13, and CML14 showed specific, high-affinity, calcium-independent binding to the IQ domains of myosin VIIIs. CaM, CML13, and CML14 co-localized to plasma membrane-bound puncta when co-expressed with red fluorescent protein-myosin fusion proteins containing IQ and tail domains of myosin VIIIs. In vitro actin motility assays using recombinant myosin VIIIs demonstrated that CaM, CML13, and CML14 function as light chains. Suppression of CML13 or CML14 expression using RNA silencing resulted in a shortened-hypocotyl phenotype, similar to that observed in a quadruple myosin mutant, myosin viii4KO. Collectively, our data indicate that Arabidopsis CML13 and CML14 are novel myosin VIII light chains.
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Affiliation(s)
- Kyle Symonds
- Department of Biology, Queen’s University, Kingston, ON, Canada
| | | | - Bryan Hau
- Department of Biology, Queen’s University, Kingston, ON, Canada
| | - Vikas Dwivedi
- Institute of Plant Sciences, Volcani Institute, ARO, Rishon LeZion 7528809, Israel
| | - Eduard Belausov
- Institute of Plant Sciences, Volcani Institute, ARO, Rishon LeZion 7528809, Israel
| | - Sefi Bar-Sinai
- Institute of Plant Sciences, Volcani Institute, ARO, Rishon LeZion 7528809, Israel
| | - Motoki Tominaga
- Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
- Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Takeshi Haraguchi
- Department of Biology, Graduate School of Science, Chiba University, Inage-ku, Chiba 263-8522, Japan
| | - Einat Sadot
- Institute of Plant Sciences, Volcani Institute, ARO, Rishon LeZion 7528809, Israel
| | - Kohji Ito
- Department of Biology, Graduate School of Science, Chiba University, Inage-ku, Chiba 263-8522, Japan
| | - Wayne A Snedden
- Department of Biology, Queen’s University, Kingston, ON, Canada
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2
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Kim C, Kim Y, Lee SJ, Yun SR, Choi J, Kim SO, Yang Y, Ihee H. Visualizing Heterogeneous Protein Conformations with Multi-Tilt Nanoparticle-Aided Cryo-Electron Microscopy Sampling. NANO LETTERS 2023; 23:3334-3343. [PMID: 37068052 PMCID: PMC10141564 DOI: 10.1021/acs.nanolett.3c00313] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Obtaining the heterogeneous conformation of small proteins is important for understanding their biological role, but it is still challenging. Here, we developed a multi-tilt nanoparticle-aided cryo-electron microscopy sampling (MT-NACS) technique that enables the observation of heterogeneous conformations of small proteins and applied it to calmodulin. By imaging the proteins labeled by two gold nanoparticles at multiple tilt angles and analyzing the projected positions of the nanoparticles, the distributions of 3D interparticle distances were obtained. From the measured distance distributions, the conformational changes associated with Ca2+ binding and salt concentration were determined. MT-NACS was also used to track the structural change accompanied by the interaction between amyloid-beta and calmodulin, which has never been observed experimentally. This work offers an alternative platform for studying the functional flexibility of small proteins.
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Affiliation(s)
- Changin Kim
- Department
of Chemistry, Korea Advanced Institute of
Science and Technology (KAIST), Daejeon 34141, Republic of Korea
- KI
for the BioCentury, Korea Advanced Institute
of Science and Technology (KAIST), Daejeon 34141, Republic
of Korea
- Center
for Advanced Reaction Dynamics, Institute
for Basic Science (IBS), Daejeon 34141, Republic of Korea
| | - Yeeun Kim
- Department
of Physics, Korea Advanced Institute of
Science and Technology (KAIST), Daejeon 34141, Republic
of Korea
| | - Sang Jin Lee
- Department
of Chemistry, Korea Advanced Institute of
Science and Technology (KAIST), Daejeon 34141, Republic of Korea
- KI
for the BioCentury, Korea Advanced Institute
of Science and Technology (KAIST), Daejeon 34141, Republic
of Korea
- Center
for Advanced Reaction Dynamics, Institute
for Basic Science (IBS), Daejeon 34141, Republic of Korea
| | - So Ri Yun
- Department
of Chemistry, Korea Advanced Institute of
Science and Technology (KAIST), Daejeon 34141, Republic of Korea
- KI
for the BioCentury, Korea Advanced Institute
of Science and Technology (KAIST), Daejeon 34141, Republic
of Korea
- Center
for Advanced Reaction Dynamics, Institute
for Basic Science (IBS), Daejeon 34141, Republic of Korea
| | - Jungkweon Choi
- Department
of Chemistry, Korea Advanced Institute of
Science and Technology (KAIST), Daejeon 34141, Republic of Korea
- KI
for the BioCentury, Korea Advanced Institute
of Science and Technology (KAIST), Daejeon 34141, Republic
of Korea
- Center
for Advanced Reaction Dynamics, Institute
for Basic Science (IBS), Daejeon 34141, Republic of Korea
| | - Seong Ok Kim
- Department
of Chemistry, Korea Advanced Institute of
Science and Technology (KAIST), Daejeon 34141, Republic of Korea
- KI
for the BioCentury, Korea Advanced Institute
of Science and Technology (KAIST), Daejeon 34141, Republic
of Korea
- Center
for Advanced Reaction Dynamics, Institute
for Basic Science (IBS), Daejeon 34141, Republic of Korea
| | - Yongsoo Yang
- Department
of Physics, Korea Advanced Institute of
Science and Technology (KAIST), Daejeon 34141, Republic
of Korea
- Y.Y.:
email, ; tel, +82-42-350-7303
| | - Hyotcherl Ihee
- Department
of Chemistry, Korea Advanced Institute of
Science and Technology (KAIST), Daejeon 34141, Republic of Korea
- KI
for the BioCentury, Korea Advanced Institute
of Science and Technology (KAIST), Daejeon 34141, Republic
of Korea
- Center
for Advanced Reaction Dynamics, Institute
for Basic Science (IBS), Daejeon 34141, Republic of Korea
- H.I.: email, ; tel, +82-42-350-2844
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3
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Stewart AM, Shanmugam M, Kutta RJ, Scrutton NS, Lovett JE, Hay S. Combined Pulsed Electron Double Resonance EPR and Molecular Dynamics Investigations of Calmodulin Suggest Effects of Crowding Agents on Protein Structures. Biochemistry 2022; 61:1735-1742. [PMID: 35979922 PMCID: PMC9454100 DOI: 10.1021/acs.biochem.2c00099] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Calmodulin (CaM) is a highly dynamic Ca2+-binding
protein
that exhibits large conformational changes upon binding Ca2+ and target proteins. Although it is accepted that CaM exists in
an equilibrium of conformational states in the absence of target protein,
the physiological relevance of an elongated helical linker region
in the Ca2+-replete form has been highly debated. In this
study, we use PELDOR (pulsed electron–electron double resonance)
EPR measurements of a doubly spin-labeled CaM variant to assess the
conformational states of CaM in the apo-, Ca2+-bound, and
Ca2+ plus target peptide-bound states. Our findings are
consistent with a three-state conformational model of CaM, showing
a semi-open apo-state, a highly extended Ca2+-replete state,
and a compact target protein-bound state. Molecular dynamics simulations
suggest that the presence of glycerol, and potentially other molecular
crowding agents, has a profound effect on the relative stability of
the different conformational states. Differing experimental conditions
may explain the discrepancies in the literature regarding the observed
conformational state(s) of CaM, and our PELDOR measurements show good
evidence for an extended conformation of Ca2+-replete CaM
similar to the one observed in early X-ray crystal structures.
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Affiliation(s)
- Andrew M Stewart
- The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames 50011, Iowa, United States.,Manchester Institute of Biotechnology and Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
| | - Muralidharan Shanmugam
- Manchester Institute of Biotechnology and Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
| | - Roger J Kutta
- Manchester Institute of Biotechnology and Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.,Institute of Physical and Theoretical Chemistry, University of Regensburg, Regensburg 93040, Germany
| | - Nigel S Scrutton
- Manchester Institute of Biotechnology and Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
| | - Janet E Lovett
- SUPA School of Physics and Astronomy and BSRC, The University of St Andrews, St Andrews KY16 9SS, U.K
| | - Sam Hay
- Manchester Institute of Biotechnology and Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
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4
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Jalalypour F, Sensoy O, Atilgan C. Perturb-Scan-Pull: A Novel Method Facilitating Conformational Transitions in Proteins. J Chem Theory Comput 2020; 16:3825-3841. [PMID: 32324386 DOI: 10.1021/acs.jctc.9b01222] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Conformational transitions in proteins facilitate precise physiological functions. Therefore, it is crucial to understand the mechanisms underlying these processes to modulate protein function. Yet, studying structural and dynamical properties of proteins is notoriously challenging due to the complexity of the underlying potential energy surfaces (PES). We have previously developed the perturbation-response scanning (PRS) method to identify key residues that participate in the communication network responsible for specific conformational transitions. PRS is based on a residue-by-residue scan of the protein to determine the subset of residues/forces which provide the closest conformational change leading to a target conformational state, inasmuch as linear response theory applies to these motions. Here, we develop a novel method to further evaluate if conformational transitions may be triggered on the PES. We aim to study functionally relevant conformational transitions in proteins by using results obtained from PRS and feeding them as inputs to steered molecular dynamics simulations. The success and the transferability of the method are evaluated on three protein systems having different complexities of motion on the PES: calmodulin, adenylate kinase, and bacterial ferric binding protein. We find that the method captures the target conformation, while providing key residues and the optimum paths with relatively low free energy profiles.
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Affiliation(s)
- Farzaneh Jalalypour
- Faculty of Engineering and Natural Sciences, Sabanci University, 34956, Istanbul, Turkey
| | - Ozge Sensoy
- School of Engineering and Natural Sciences, Istanbul Medipol University, 34810, Istanbul, Turkey
| | - Canan Atilgan
- Faculty of Engineering and Natural Sciences, Sabanci University, 34956, Istanbul, Turkey.,Sabanci University Nanotechnology Research and Application Center, SUNUM, 34956, Istanbul, Turkey
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5
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McCarthy MR, Savich Y, Cornea RL, Thomas DD. Resolved Structural States of Calmodulin in Regulation of Skeletal Muscle Calcium Release. Biophys J 2020; 118:1090-1100. [PMID: 32049056 DOI: 10.1016/j.bpj.2020.01.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 12/20/2019] [Accepted: 01/06/2020] [Indexed: 12/22/2022] Open
Abstract
Calmodulin (CaM) is proposed to modulate activity of the skeletal muscle sarcoplasmic reticulum (SR) calcium release channel (ryanodine receptor, RyR1 isoform) via a mechanism dependent on the conformation of RyR1-bound CaM. However, the correlation between CaM structure and functional regulation of RyR in physiologically relevant conditions is largely unknown. Here, we have used time-resolved fluorescence resonance energy transfer (TR-FRET) to study structural changes in CaM that may play a role in the regulation of RyR1. We covalently labeled each lobe of CaM (N and C) with fluorescent probes and used intramolecular TR-FRET to assess interlobe distances when CaM is bound to RyR1 in SR membranes, purified RyR1, or a peptide corresponding to the CaM-binding domain of RyR (RyRp). TR-FRET resolved an equilibrium between two distinct structural states (conformations) of CaM, each characterized by an interlobe distance and Gaussian distribution width (disorder). In isolated CaM, at low Ca2+, the two conformations of CaM are resolved, centered at 5 nm (closed) and 7 nm (open). At high Ca2+, the equilibrium shifts to favor the open conformation. In the presence of RyRp at high Ca2+, the closed conformation shifts to a more compact conformation and is the major component. When CaM is bound to full-length RyR1, either purified or in SR membranes, strikingly different results were obtained: 1) the two conformations are resolved and more ordered, 2) the open state is the major component, and 3) Ca2+ stabilized the closed conformation by a factor of two. We conclude that the Ca2+-dependent structural distribution of CaM bound to RyR1 is distinct from that of CaM bound to RyRp. We propose that the function of RyR1 is tuned to the Ca2+-dependent structural dynamics of bound CaM.
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Affiliation(s)
- Megan R McCarthy
- Department of Biochemistry, Molecular Biology, and Biophysics, Minneapolis, Minnesota
| | - Yahor Savich
- Department of Biochemistry, Molecular Biology, and Biophysics, Minneapolis, Minnesota; School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota
| | - Razvan L Cornea
- Department of Biochemistry, Molecular Biology, and Biophysics, Minneapolis, Minnesota
| | - David D Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, Minneapolis, Minnesota.
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6
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Sadoine M, Cerminara M, Gerrits M, Fitter J, Katranidis A. Cotranslational Incorporation into Proteins of a Fluorophore Suitable for smFRET Studies. ACS Synth Biol 2018; 7:405-411. [PMID: 29370697 DOI: 10.1021/acssynbio.7b00433] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Single-molecule FRET (smFRET) is a powerful tool to investigate conformational changes of biological molecules. In general, smFRET studies require protein samples that are site-specifically double-labeled with a pair of donor and acceptor fluorophores. The common approaches to produce such samples cannot be applied when studying the synthesis and folding of the polypeptide chain on the ribosome. The best strategy is to incorporate two fluorescent amino acids cotranslationally using cell-free protein synthesis systems. Here, we demonstrate the cotranslational site-specific incorporation into a model protein of Atto633, a dye with excellent photophysical properties, suitable for single molecule spectroscopy, together with a second dye using a combination of the sense cysteine and the nonsense amber codon. In this work we show that cotranslational incorporation of good fluorophores into proteins is a viable strategy to produce suitable samples for smFRET studies.
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Affiliation(s)
- Mayuri Sadoine
- Forschungszentrum Jülich, Institute of Complex Systems
ICS-5, 52428 Jülich, Germany
| | - Michele Cerminara
- Forschungszentrum Jülich, Institute of Complex Systems
ICS-5, 52428 Jülich, Germany
| | - Michael Gerrits
- Biocatalysis
Group, Department of Chemistry, Technische Universität Berlin, 10623 Berlin, Germany
| | - Jörg Fitter
- Forschungszentrum Jülich, Institute of Complex Systems
ICS-5, 52428 Jülich, Germany
- RWTH Aachen University, I.Physikalisches
Institut (IA), 52062 Aachen, Germany
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7
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Sadoine M, Cerminara M, Kempf N, Gerrits M, Fitter J, Katranidis A. Selective Double-Labeling of Cell-Free Synthesized Proteins for More Accurate smFRET Studies. Anal Chem 2017; 89:11278-11285. [DOI: 10.1021/acs.analchem.7b01639] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mayuri Sadoine
- Forschungszentrum
Jülich, Institute of Complex Systems ICS-5, 52425 Jülich, Germany
| | - Michele Cerminara
- Forschungszentrum
Jülich, Institute of Complex Systems ICS-5, 52425 Jülich, Germany
| | - Noémie Kempf
- Forschungszentrum
Jülich, Institute of Complex Systems ICS-5, 52425 Jülich, Germany
| | | | - Jörg Fitter
- Forschungszentrum
Jülich, Institute of Complex Systems ICS-5, 52425 Jülich, Germany
- 1. Physikalisches
Institut (IA), RWTH Aachen, 52062 Aachen, Germany
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8
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Single molecule fluorescence spectroscopy for quantitative biological applications. QUANTITATIVE BIOLOGY 2016. [DOI: 10.1007/s40484-016-0083-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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9
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DeVore MS, Braimah A, Benson DR, Johnson CK. Single-Molecule FRET States, Conformational Interchange, and Conformational Selection by Dye Labels in Calmodulin. J Phys Chem B 2016; 120:4357-64. [PMID: 27111039 DOI: 10.1021/acs.jpcb.6b00864] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We investigate the roles of measurement time scale and the nature of the fluorophores in the FRET states measured for calmodulin, a calcium signaling protein known to undergo pronounced conformational changes. The measured FRET distributions depend markedly on the measurement time scale (nanosecond or microsecond). Comparison of FRET distributions measured by donor fluorescence decay with FRET distributions recovered from single-molecule burst measurements binned over time scales of 90 μs to 1 ms reveals conformational averaging over the intervening time regimes. We find further that, particularly in the presence of saturating Ca(2+), the nature of the measured single-molecule FRET distribution depends markedly on the identity of the FRET pair. The results suggest interchange between conformational states on time scales of hundreds of microseconds or less. Interaction with a fluorophore such as the dye Texas Red alters both the nature of the measured FRET distributions and the dynamics of conformational interchange. The results further suggest that the fluorophore may not be merely a benign reporter of protein conformations in FRET studies, but may in fact alter the conformational landscape.
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Affiliation(s)
- Matthew S DeVore
- Department of Chemistry, University of Kansas , Lawrence, Kansas 66045, United States
| | - Adebayo Braimah
- Department of Chemistry, University of Kansas , Lawrence, Kansas 66045, United States
| | - David R Benson
- Department of Chemistry, University of Kansas , Lawrence, Kansas 66045, United States
| | - Carey K Johnson
- Department of Chemistry, University of Kansas , Lawrence, Kansas 66045, United States
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10
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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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11
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Yuan H, Xing C, An H, Niu R, Li R, Yan W, Zhan Y. Ca2+-controlled assembly for visualized detection of conformation changes of calmodulin. ACS APPLIED MATERIALS & INTERFACES 2014; 6:14790-14794. [PMID: 25151856 DOI: 10.1021/am504729d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A new strategy has been designed for visualized detection of the conformation changes of calmodulin bound to target peptide (CaM-M13) based on the conformation sensitive property of a water-soluble conjugated polythiophene derivative (PMNT) and the electrostatic interactions of PMNT/CaM-M13. Interestingly, the direct visualized PMNT color changes under UV irradiation and the turbidity changes of samples in aqueous medium can be applied to detect the conformation changes as well as the controllable assembly of PMNT/CaM-M13 with Ca(2+) in aqueous medium. Because of the specific binding of Ca(2+), the assembly of PMNT/CaM-M13 can be applied to sense calcium as well.
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Affiliation(s)
- Hongbo Yuan
- Key Laboratory of Hebei Province for Molecular Biophysics, Institute of Biophysics, Hebei University of Technology , Tianjin 300401, P. R. China
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12
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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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13
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Clore GM. Interplay between conformational selection and induced fit in multidomain protein-ligand binding probed by paramagnetic relaxation enhancement. Biophys Chem 2013; 186:3-12. [PMID: 24070540 DOI: 10.1016/j.bpc.2013.08.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 08/24/2013] [Accepted: 08/24/2013] [Indexed: 11/29/2022]
Abstract
The binding of ligands and substrates to proteins has been extensively studied for many years and can be described, in its simplest form, by two limiting mechanisms: conformational selection and induced fit. Conformational selection involves the binding of ligand to a pre-existing sparsely-populated conformation of the free protein that is the same as that in the final protein-ligand complex. In the case of induced fit, the ligand binds to the major conformation of the free protein and only subsequent to binding undergoes a conformational change to the final protein-ligand complex. While these two mechanisms can be dissected and distinguished by transient kinetic measurements, direct direction, characterization and visualization of transient, sparsely-populated states of proteins are experimentally challenging. Unless trapped, sparsely-populated states are generally invisible to conventional structural and biophysical techniques, including crystallography and most NMR measurements. In this review we summarize some recent developments in the use of paramagnetic relaxation enhancement to directly study sparsely-populated states of proteins and illustrate the application of this approach to two proteins, maltose binding protein and calmodulin, both of which undergo large rigid body conformational rearrangements upon ligand binding from an open apo state to a closed ligand-bound holo state. We show that the apo state ensemble comprises a small population of partially-closed configurations that are similar but not identical to that of the holo state. These results highlight the complementarity and interplay of induced fit and conformational selection and suggest that the existence of partially-closed states in the absence of ligand facilitates the transition to the closed ligand-bound state.
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Affiliation(s)
- G Marius Clore
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA.
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14
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Lerner E, Hilzenrat G, Amir D, Tauber E, Garini Y, Haas E. Preparation of homogeneous samples of double-labelled protein suitable for single-molecule FRET measurements. Anal Bioanal Chem 2013; 405:5983-91. [DOI: 10.1007/s00216-013-7002-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Revised: 04/15/2013] [Accepted: 04/18/2013] [Indexed: 10/26/2022]
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15
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Hellstrand E, Kukora S, Shuman CF, Steenbergen S, Thulin E, Kohli A, Krouse B, Linse S, Åkerfeldt KS. Förster resonance energy transfer studies of calmodulin produced by native protein ligation reveal inter-domain electrostatic repulsion. FEBS J 2013; 280:2675-87. [DOI: 10.1111/febs.12269] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 03/11/2013] [Accepted: 03/26/2013] [Indexed: 12/15/2022]
Affiliation(s)
- Erik Hellstrand
- Biophysical Chemistry, Chemical Centre; Lund University; Sweden
| | | | | | | | - Eva Thulin
- Biochemistry and Structural Biology, Chemical Centre; Lund University; Sweden
| | - Anita Kohli
- Department of Chemistry; Haverford College; PA; USA
| | - Beth Krouse
- Department of Chemistry; Haverford College; PA; USA
| | - Sara Linse
- Biochemistry and Structural Biology, Chemical Centre; Lund University; Sweden
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16
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Noshiro D, Sonomura K, Yu HH, Imanishi M, Asami K, Futaki S. Construction of a Ca(2+)-gated artificial channel by fusing alamethicin with a calmodulin-derived extramembrane segment. Bioconjug Chem 2013; 24:188-95. [PMID: 23272973 DOI: 10.1021/bc300468x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Using native chemical ligation, we constructed a Ca(2+)-gated fusion channel protein consisting of alamethicin and the C-terminal domain of calmodulin. At pH 5.4 and in the absence of Ca(2+), this fusion protein yielded a burst-like channel current with no discrete channel conductance levels. However, Ca(2+) significantly lengthened the specific channel open state and increased the mean channel current, while Mg(2+) produced no significant changes in the channel current. On the basis of 8-anilinonaphthalene-1-sulfonic acid (ANS) fluorescent measurement, Ca(2+)-stimulated gating may be related to an increased surface hydrophobicity of the extramembrane segment of the fusion protein.
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Affiliation(s)
- Daisuke Noshiro
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
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17
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Wang L, Witham S, Zhang Z, Li L, Hodsdon ME, Alexov E. In silico investigation of pH-dependence of prolactin and human growth hormone binding to human prolactin receptor. COMMUNICATIONS IN COMPUTATIONAL PHYSICS 2013; 13:207-222. [PMID: 24683423 PMCID: PMC3966486 DOI: 10.4208/cicp.170911.131011s] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Experimental data shows that the binding of human prolactin (hPRL) to human prolactin receptor (hPRLr-ECD) is strongly pH-dependent, while the binding of the same receptor to human growth hormone (hGH) is pH-independent. Here we carry in silico analysis of the molecular effects causing such a difference and reveal the role of individual amino acids. It is shown that the computational modeling correctly predicts experimentally determined pKa's of histidine residues in an unbound state in the majority of the cases and the pH-dependence of the binding free energy. Structural analysis carried in conjunction with calculated pH-dependence of the binding revealed that the main reason for pH-dependence of the binding of hPRL-hPRLr-ECD is a number of salt- bridges across the interface of the complex, while no salt-bridges are formed in the hGH-hPRlr-ECD. Specifically, most of the salt-bridges involve histidine residues and this is the reason for the pH-dependence across a physiological range of pH. The analysis not only revealed the molecular mechanism of the pH-dependence of the hPRL-hPRLr-ECD, but also provided critical insight into the underlying physic-chemical mechanism.
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Affiliation(s)
- Lin Wang
- Computational Biophysics and Bioinformatics, Department of Physics, Clemson University, Clemson, SC 29634
| | - Shawn Witham
- Computational Biophysics and Bioinformatics, Department of Physics, Clemson University, Clemson, SC 29634
| | - Zhe Zhang
- Computational Biophysics and Bioinformatics, Department of Physics, Clemson University, Clemson, SC 29634
| | - Lin Li
- Computational Biophysics and Bioinformatics, Department of Physics, Clemson University, Clemson, SC 29634
| | - Michael E. Hodsdon
- Department of Laboratory Medicine and the Department of Pharmacology, Yale School of Medicine, New Haven, Connecticut 06520
| | - Emil Alexov
- Computational Biophysics and Bioinformatics, Department of Physics, Clemson University, Clemson, SC 29634
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18
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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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19
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Abstract
The role of electrostatics in protein-protein interactions and binding is reviewed in this paper. A brief outline of the computational modeling, in the framework of continuum electrostatics, is presented and the basic electrostatic effects occurring upon the formation of the complex are discussed. The effect of the salt concentration and pH of the water phase on protein-protein binding free energy is demonstrated which indicates that the increase of the salt concentration tends to weaken the binding, an observation that is attributed to the optimization of the charge-charge interactions across the interface. It is pointed out that the pH-optimum (pH of optimal binding affinity) varies among the protein-protein complexes, and perhaps is a result of their adaptation to particular subcellular compartments. The similarities and differences between hetero- and homo-complexes are outlined and discussed with respect to the binding mode and charge complementarity.
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Affiliation(s)
- Zhe Zhang
- Computational Biophysics and Bioinformatics, Department of Physics, Clemson University, Clemson,SC 29634, USA
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20
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Snijder J, Rose RJ, Raijmakers R, Heck AJ. Site-specific methionine oxidation in calmodulin affects structural integrity and interaction with Ca2+/calmodulin-dependent protein kinase II. J Struct Biol 2011; 174:187-95. [DOI: 10.1016/j.jsb.2010.12.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 12/02/2010] [Accepted: 12/08/2010] [Indexed: 10/18/2022]
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21
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Price ES, DeVore MS, Johnson CK. Detecting intramolecular dynamics and multiple Förster resonance energy transfer states by fluorescence correlation spectroscopy. J Phys Chem B 2010; 114:5895-902. [PMID: 20392129 DOI: 10.1021/jp912125z] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Fluorescence correlation spectroscopy (FCS) is a robust method for the detection of intramolecular dynamics in proteins but is also susceptible to interference from other dynamic processes such as triplet kinetics and photobleaching. We describe an approach for the detection of intramolecular dynamics in proteins labeled with a FRET dye pair based on global fitting to the two autocorrelation functions (green-green and red-red) and the two cross-correlation functions (green-red and red-green). We applied the method to detect intramolecular dynamics in the Ca(2+) signaling protein calmodulin. Dynamics were detected on the 100 mus time scale in Ca(2+)-activated calmodulin, whereas in apocalmodulin dynamics were not detected on this time scale. Control measurements on a polyproline FRET construct (Gly-Pro(15)-Cys) demonstrate the reliability of the method for isolating intramolecular dynamics from other dynamic processes on the microsecond time scale and confirm the absence of intramolecular dynamics of polyproline. We further show the sensitivity of the initial amplitudes of the FCS auto- and cross-correlation functions to the presence of multiple FRET states, static or dynamic. The FCS measurements also show that the diffusion of Ca(2+)-calmodulin is slower than that of apocalmodulin, indicating either a larger average hydrodynamic radius or shape effects resulting in a slower translational diffusion.
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Affiliation(s)
- E Shane Price
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, USA
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22
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Timsit Y, Acosta Z, Allemand F, Chiaruttini C, Springer M. The role of disordered ribosomal protein extensions in the early steps of eubacterial 50 S ribosomal subunit assembly. Int J Mol Sci 2009; 10:817-834. [PMID: 19399222 PMCID: PMC2672003 DOI: 10.3390/ijms10030817] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Revised: 02/23/2009] [Accepted: 02/24/2009] [Indexed: 12/23/2022] Open
Abstract
Although during the past decade research has shown the functional importance of disorder in proteins, many of the structural and dynamics properties of intrinsically unstructured proteins (IUPs) remain to be elucidated. This review is focused on the role of the extensions of the ribosomal proteins in the early steps of the assembly of the eubacterial 50 S subunit. The recent crystallographic structures of the ribosomal particles have revealed the picture of a complex assembly pathway that condenses the rRNA and the ribosomal proteins into active ribosomes. However, little is know about the molecular mechanisms of this process. It is thought that the long basic r-protein extensions that penetrate deeply into the subunit cores play a key role through disorder-order transitions and/or co-folding mechanisms. A current view is that such structural transitions may facilitate the proper rRNA folding. In this paper, the structures of the proteins L3, L4, L13, L20, L22 and L24 that have been experimentally found to be essential for the first steps of ribosome assembly have been compared. On the basis of their structural and dynamics properties, three categories of extensions have been identified. Each of them seems to play a distinct function. Among them, only the coil-helix transition that occurs in a phylogenetically conserved cluster of basic residues of the L20 extension appears to be strictly required for the large subunit assembly in eubacteria. The role of alpha helix-coil transitions in 23 S RNA folding is discussed in the light of the calcium binding protein calmodulin that shares many structural and dynamics properties with L20.
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Affiliation(s)
- Youri Timsit
- Laboratoire de Cristallographie, Institut de Biologie Physico-Chimique CNRS, 13, rue Pierre et Marie Curie, 75005 Paris, France; E-Mail:
- Author to whom correspondence should be addressed; E-mail:
; Tel. +01-58-41-51-66
| | - Zahir Acosta
- Laboratoire de Cristallographie, Institut de Biologie Physico-Chimique CNRS, 13, rue Pierre et Marie Curie, 75005 Paris, France; E-Mail:
| | - Frédéric Allemand
- Laboratoire de Biochimie, Institut de Biologie Physico-Chimique CNRS, 13, rue Pierre et Marie Curie, 75005 Paris, France; E-Mail:
(F.A.);
(C.C.);
(M.S.)
| | - Claude Chiaruttini
- Laboratoire de Biochimie, Institut de Biologie Physico-Chimique CNRS, 13, rue Pierre et Marie Curie, 75005 Paris, France; E-Mail:
(F.A.);
(C.C.);
(M.S.)
| | - Mathias Springer
- Laboratoire de Biochimie, Institut de Biologie Physico-Chimique CNRS, 13, rue Pierre et Marie Curie, 75005 Paris, France; E-Mail:
(F.A.);
(C.C.);
(M.S.)
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23
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Strunk JJ, Gregor I, Becker Y, Lamken P, Lata S, Reichel A, Enderlein J, Piehler J. Probing Protein Conformations by in Situ Non-Covalent Fluorescence Labeling. Bioconjug Chem 2008; 20:41-6. [DOI: 10.1021/bc8002088] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jennifer Julia Strunk
- Institute of Biochemistry and Cluster of Excellence Macromolecular Complexes (CEF), Johann Wolfgang Goethe-University, Frankfurt/Main, Germany, Department of Molecular Neurosensorics, Caesar Research Centre, Bonn, Germany, and Institute of Physical and Theoretical Chemistry, Eberhard-Karls-University, Tübingen, Germany
| | - Ingo Gregor
- Institute of Biochemistry and Cluster of Excellence Macromolecular Complexes (CEF), Johann Wolfgang Goethe-University, Frankfurt/Main, Germany, Department of Molecular Neurosensorics, Caesar Research Centre, Bonn, Germany, and Institute of Physical and Theoretical Chemistry, Eberhard-Karls-University, Tübingen, Germany
| | - Yvonne Becker
- Institute of Biochemistry and Cluster of Excellence Macromolecular Complexes (CEF), Johann Wolfgang Goethe-University, Frankfurt/Main, Germany, Department of Molecular Neurosensorics, Caesar Research Centre, Bonn, Germany, and Institute of Physical and Theoretical Chemistry, Eberhard-Karls-University, Tübingen, Germany
| | - Peter Lamken
- Institute of Biochemistry and Cluster of Excellence Macromolecular Complexes (CEF), Johann Wolfgang Goethe-University, Frankfurt/Main, Germany, Department of Molecular Neurosensorics, Caesar Research Centre, Bonn, Germany, and Institute of Physical and Theoretical Chemistry, Eberhard-Karls-University, Tübingen, Germany
| | - Suman Lata
- Institute of Biochemistry and Cluster of Excellence Macromolecular Complexes (CEF), Johann Wolfgang Goethe-University, Frankfurt/Main, Germany, Department of Molecular Neurosensorics, Caesar Research Centre, Bonn, Germany, and Institute of Physical and Theoretical Chemistry, Eberhard-Karls-University, Tübingen, Germany
| | - Annett Reichel
- Institute of Biochemistry and Cluster of Excellence Macromolecular Complexes (CEF), Johann Wolfgang Goethe-University, Frankfurt/Main, Germany, Department of Molecular Neurosensorics, Caesar Research Centre, Bonn, Germany, and Institute of Physical and Theoretical Chemistry, Eberhard-Karls-University, Tübingen, Germany
| | - Jörg Enderlein
- Institute of Biochemistry and Cluster of Excellence Macromolecular Complexes (CEF), Johann Wolfgang Goethe-University, Frankfurt/Main, Germany, Department of Molecular Neurosensorics, Caesar Research Centre, Bonn, Germany, and Institute of Physical and Theoretical Chemistry, Eberhard-Karls-University, Tübingen, Germany
| | - Jacob Piehler
- Institute of Biochemistry and Cluster of Excellence Macromolecular Complexes (CEF), Johann Wolfgang Goethe-University, Frankfurt/Main, Germany, Department of Molecular Neurosensorics, Caesar Research Centre, Bonn, Germany, and Institute of Physical and Theoretical Chemistry, Eberhard-Karls-University, Tübingen, Germany
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24
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Spratt DE, Taiakina V, Palmer M, Guillemette JG. FRET conformational analysis of calmodulin binding to nitric oxide synthase peptides and enzymes. Biochemistry 2008; 47:12006-17. [PMID: 18947187 DOI: 10.1021/bi801418s] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Calmodulin (CaM) is a ubiquitous Ca (2+)-sensor protein that binds and activates the nitric oxide synthase (NOS) enzymes. We have used fluorescence resonance energy transfer (FRET) to examine the conformational transitions of CaM induced by its binding to synthetic nitric oxide synthase (NOS) CaM-binding domain peptides and full length heme-free constitutive NOS (cNOS) enzymes over a range of physiologically relevant free Ca (2+) concentrations. We demonstrate for the first time that the domains of CaM collapse when associated with Ca (2+)-independent inducible NOS CaM-binding domain, similar to the previously solved crystal structures of CaM bound to the Ca (2+)-dependent cNOS peptides. We show that the association of CaM is not detectable with the cNOS peptides at low free Ca (2+) concentrations (<40 nM). In contrast, we demonstrate that CaM associates with the cNOS holo-enzymes in the absence of Ca (2+) and that the Ca (2+)-dependent transition occurs at a lower free Ca (2+) concentration with the cNOS holo-enzymes. Our results suggest that other regions outside of the CaM-binding domain in the cNOS enzymes are involved in the recruitment and binding of CaM. We also demonstrate that CaM binds to the cNOS enzymes in a sequential manner with the Ca (2+)-replete C-lobe binding first followed by the Ca (2+)-replete N-lobe. This novel FRET study helps to clarify some of the observed similarities and differences between the Ca (2+)-dependent/independent interaction between CaM and the NOS isozymes.
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Affiliation(s)
- Donald E Spratt
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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25
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Priddy TS, Price ES, Johnson CK, Carlson GM. Single molecule analyses of the conformational substates of calmodulin bound to the phosphorylase kinase complex. Protein Sci 2007; 16:1017-23. [PMID: 17525461 PMCID: PMC2206654 DOI: 10.1110/ps.062747407] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The four integral delta subunits of the phosphorylase kinase (PhK) complex are identical to calmodulin (CaM) and confer Ca(2+) sensitivity to the enzyme, but bind independently of Ca(2+). In addition to binding Ca(2+), an obligatory activator of PhK's phosphoryltransferase activity, the delta subunits transmit allosteric signals to PhK's remaining alpha, beta, and gamma subunits in activating the enzyme. Under mild conditions about 10% of the delta subunits can be exchanged for exogenous CaM. In this study, a CaM double-mutant derivatized with a fluorescent donor-acceptor pair (CaM-DA) was exchanged for delta to assess the conformational substates of PhKdelta by single molecule fluorescence resonance energy transfer (FRET) +/-Ca(2+). The exchanged subunits were determined to occupy distinct conformations, depending on the absence or presence of Ca(2+), as observed by alterations of the compact, mid-length, and extended populations of their FRET distance distributions. Specifically, the combined predominant mid-length and less common compact conformations of PhKdelta became less abundant in the presence of Ca(2+), with the delta subunits assuming more extended conformations. This behavior is in contrast to the compact forms commonly observed for many of CaM's Ca(2+)-dependent interactions with other proteins. In addition, the conformational distributions of the exchanged PhKdelta subunits were distinct from those of CaM-DA free in solution, +/-Ca(2+), as well as from exogenous CaM bound to the PhK complex as delta'. The distinction between delta and delta' is that the latter binds only in the presence of Ca(2+), but stoichiometrically and at a different location in the complex than delta.
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Affiliation(s)
- Timothy S Priddy
- Department of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110, USA
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26
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Juranić N, Atanasova E, Streiff JH, Macura S, Prendergast FG. Solvent-induced differentiation of protein backbone hydrogen bonds in calmodulin. Protein Sci 2007; 16:1329-37. [PMID: 17567747 PMCID: PMC2206704 DOI: 10.1110/ps.062689807] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2006] [Revised: 02/18/2007] [Accepted: 02/23/2007] [Indexed: 10/23/2022]
Abstract
In apo and holoCaM, almost half of the hydrogen bonds (H-bonds) at the protein backbone expected from the corresponding NMR or X-ray structures were not detected by h3JNC' couplings. The paucity of the h3JNC' couplings was considered in terms of dynamic features of these structures. We examined a set of seven proteins and found that protein-backbone H-bonds form two groups according to the h3JNC' couplings measured in solution. H-bonds that have h3JNC' couplings above the threshold of 0.2 Hz show distance/angle correlation among the H-bond geometrical parameters, and appear to be supported by the backbone dynamics in solution. The other H-bonds have no such correlation; they populate the water-exposed and flexible regions of proteins, including many of the CaM helices. The observed differentiation in a dynamical behavior of backbone H-bonds in apo and holoCaM appears to be related to protein functions.
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Affiliation(s)
- Nenad Juranić
- Department of Biochemistry and Molecular Biology, Mayo College of Medicine, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
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27
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Slaughter BD, Bieber-Urbauer RJ, Johnson CK. Single-molecule tracking of sub-millisecond domain motion in calmodulin. J Phys Chem B 2007; 109:12658-62. [PMID: 16852567 DOI: 10.1021/jp051666o] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We used single-pair fluorescence resonance energy transfer (spFRET) to track distance changes between domains of fluorescently labeled calmodulin (CaM) on the sub-millisecond time scale. In most cases, CaM remained in the same conformational substate over time periods of up to 1 ms, showing that conformational interchange occurs on a longer time scale. However, in some instances, apparent transitions between conformational substates could be detected. The magnitude of sub-millisecond motion within the dominant conformational substate also revealed fluctuations in distance between domains that were dependent on pH and ionic strength.
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28
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Isvoran A, Craescu CT, Alexov E. Electrostatic control of the overall shape of calmodulin: numerical calculations. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2007; 36:225-37. [PMID: 17285296 DOI: 10.1007/s00249-006-0123-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Revised: 11/20/2006] [Accepted: 11/28/2006] [Indexed: 10/23/2022]
Abstract
The paper reports the results of numerical calculations of the pKa's of the ionizable groups and the electrostatic interactions between calmodulin lobes in three different states of calmodulin: calcium-free, peptide-free; calcium-loaded, peptide-free; and calcium-loaded, peptide-bound. NMR and X-ray studies revealed that in these states the overall structure of calmodulin adopts various conformations referred as: disordered semi-compact, extended and compact conformations, respectively. In addition, a new X-ray structure was recently reported (Structure, 2003, 11, 1303) showing that calcium-loaded, peptide-free calmodulin can also adopt a compact conformation in addition to the well known extended conformation. The calculated energy changes of calcium-loaded, peptide-free calmodulin along the pathway connecting these two conformations provide a possible explanation for this structural plasticity. The effect of pH and organic compounds in the solution phase on the preference of calmodulin to adopt compact or extended conformations may be thus rationalized. Analysis of the contribution of the ionization changes to the energy of association of calmodulin lobes suggested that the formation of the compact forms requires protonation of several acidic residues. However, two different protonation scenarios are revealed: a protonation due to internal lobe organization and thus independent of the lobes association, and a protonation induced by the lobes association resulting to a proton uptake. In addition, the role of the individual residues on the energy of association of calmodulin lobes is calculated in two compact conformations (peptide-free and peptide-bound) and is shown that a set of residues always plays a dominant role in inter-domain interactions.
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Affiliation(s)
- A Isvoran
- Department of Chemistry, West University of Timisoara, Pestallozi 16, 300115 Timisoara, Romania
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29
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Johnson CK. Calmodulin, conformational states, and calcium signaling. A single-molecule perspective. Biochemistry 2006; 45:14233-46. [PMID: 17128963 PMCID: PMC2533622 DOI: 10.1021/bi061058e] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Single-molecule fluorescence measurements can provide a new perspective on the conformations, dynamics, and interactions of proteins. Recent examples are described illustrating the application of single-molecule fluorescence spectroscopy to calcium signaling proteins with an emphasis on the new information available in single-molecule fluorescence burst measurements, resonance energy transfer, and polarization modulation methods. Calcium signaling pathways are crucial in many cellular processes. The calcium binding protein calmodulin (CaM) serves as a molecular switch to regulate a network of calcium signaling pathways. Single-molecule spectroscopic methods can yield insights into conformations and dynamics of CaM and CaM-regulated proteins. Examples include studies of the conformations and dynamics of CaM, binding of target peptides, and interaction with the plasma-membrane Ca2+ pump. Single-molecule resonance energy transfer measurements revealed conformational substates of CaM, and single-molecule polarization modulation spectroscopy was used to probe interactions between CaM and the plasma-membrane Ca2+-ATPase.
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Affiliation(s)
- Carey K Johnson
- Department of Chemistry, 1251 Wescoe Drive, University of Kansas, Lawrence, Kansas 66045-7582, USA.
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30
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Timsit Y, Allemand F, Chiaruttini C, Springer M. Coexistence of two protein folding states in the crystal structure of ribosomal protein L20. EMBO Rep 2006; 7:1013-8. [PMID: 16977336 PMCID: PMC1618378 DOI: 10.1038/sj.embor.7400803] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Revised: 08/03/2006] [Accepted: 08/03/2006] [Indexed: 11/08/2022] Open
Abstract
The recent finding of intrinsically unstructured proteins defies the classical structure-function paradigm. However, owing to their flexibility, intrinsically unstructured proteins generally escape detailed structural investigations. Consequently little is known about the extent of conformational disorder and its role in biological functions. Here, we present the X-ray structure of the unbound ribosomal protein L20, the long basic amino-terminal extension of which has been previously interpreted as fully disordered in the absence of RNA. This study provides the first detailed picture of two protein folding states trapped together in a crystal and indicates that unfolding occurs in discrete regions of the whole protein, corresponding mainly to RNA-binding residues. The electrostatic destabilization of the long alpha-helix and a structural communication between the two L20 domains are reminiscent of those observed in calmodulin. The detailed comparison of the two conformations observed in the crystal provides new insights into the role of unfolded extensions in ribosomal assembly.
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Affiliation(s)
- Youri Timsit
- Laboratoire de Cristallographie UPR9080, Institut de Biologie Physico-Chimique CNRS, 13, rue Pierre et Marie Curie, Paris 75005, France.
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31
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Watkins LP, Chang H, Yang H. Quantitative Single-Molecule Conformational Distributions: A Case Study with Poly-(l-proline). J Phys Chem A 2006; 110:5191-203. [PMID: 16610843 DOI: 10.1021/jp055886d] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Precise measurement of the potential of mean force is necessary for a fundamental understanding of the dynamics and chemical reactivity of a biological macromolecule. The unique advantage provided by the recently developed constant-information approach to analyzing time-dependent single-molecule fluorescence measurements was used with maximum entropy deconvolution to create a procedure for the accurate determination of molecular conformational distributions, and analytical expressions for the errors in these distributions were derived. This new method was applied to a derivatized poly(L-proline) series, P(n)CG3K(biotin) (n = 8, 12, 15, 18, and 24), using a modular, server-based single-molecule spectrometer that is capable of registering photon arrival times with a continuous-wave excitation source. To account for potential influence from the microscopic environment, factors that were calibrated and corrected molecule by molecule include background, cross-talk, and detection efficiency. For each single poly(L-proline) molecule, sharply peaked Förster type resonance energy transfer (FRET) efficiency and distance distributions were recovered, indicating a static end-to-end distance on the time scale of measurement. The experimental distances were compared with models of varying rigidity. The results suggest that the 23 angstroms persistence length wormlike chain model derived from experiments with high molecular weight poly(L-proline) is applicable to short chains as well.
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Affiliation(s)
- Lucas P Watkins
- Department of Chemistry, University of California at Berkeley, and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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32
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Lee S, Arunkumar AI, Chen X, Giedroc DP. Structural Insights into Homo- and Heterotropic Allosteric Coupling in the Zinc Sensor S. aureus CzrA from Covalently Fused Dimers. J Am Chem Soc 2006; 128:1937-47. [PMID: 16464095 DOI: 10.1021/ja0546828] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The Zn(II)/Co(II)-sensing transcriptional repressor, Staphylococcus aureus CzrA, is a homodimer containing a symmetry-related pair of subunit-bridging tetrahedral N(3)O metal sensor coordination sites. A metal-induced quaternary structural change within the homodimer is thought to govern the biological activity of this and other metal sensor proteins. Here, we exploit covalent (Gly(4)Ser)(n)() linkers of variable length in "fused" CzrAs, where n = 1 (designated 5L-fCzrA), 2 (10L-fCzrA), or 3 (15L-fCzrA), as molecular rulers designed to restrict any quaternary structural changes that are associated with metal binding and metal-mediated allosteric regulation of DNA binding to varying degrees. While 15L-fCzrA exhibits properties most like homodimeric CzrA, shortening the linker in 10L-fCzrA abolishes negative homotropic cooperativity of Zn(II) binding and reduces DNA binding affinity of the apoprotein significantly. Decreasing the linker length further in 5L-fCzrA effectively destroys one metal site altogether and further reduces DNA binding affinity. However, Zn(II) negatively regulates DNA binding of all fCzrAs, with allosteric coupling free energies (DeltaG(1)(c)) of 4.6, 3.1, and 2.7 kcal mol(-1) for 15L-, 10L-, and 5L-fCzrAs, respectively. Introduction of a single nonliganding H97N substitution into either the N-terminal or C-terminal protomer domain in 10L-fCzrA results in DeltaG(1)(c) = 2.6 kcal mol(-1) or approximately 83% that of 10L-fCzrA; in contrast, homodimeric H97N CzrA gives DeltaG(1)(c) = 0. (1)H-(15)N HSQC spectra acquired for wt-, 10L-fCzrA and H97N 10L-fCzrA in various Zn(II) ligation states reveal that the allosteric change of the protomer domains within the fused dimer is independent and not concerted. Thus, occupancy of a single metal site by Zn(II) introduces asymmetry into the CzrA homodimer that leads to significant allosteric regulation of DNA binding.
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Affiliation(s)
- Sunbae Lee
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128, USA
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Slaughter BD, Unruh JR, Price ES, Huynh JL, Bieber Urbauer RJ, Johnson CK. Sampling unfolding intermediates in calmodulin by single-molecule spectroscopy. J Am Chem Soc 2005; 127:12107-14. [PMID: 16117552 DOI: 10.1021/ja0526315] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We used single-pair fluorescence resonance energy transfer (spFRET) measurements to characterize denatured and partially denatured states of the multidomain calcium signaling protein calmodulin (CaM) in both its apo and Ca(2+)-bound forms. The results demonstrate the existence of an unfolding intermediate. A CaM mutant (CaM-T34C-T110C) was doubly labeled with fluorescent probes AlexaFlour 488 and Texas Red at opposing globular domains. Single-molecule distributions of the distance between fluorophores were obtained by spFRET at varying levels of the denaturant urea. Multiple conformational states of CaM were observed, and the amplitude of each conformation was dependent on urea concentration, with the amplitude of an extended conformation increasing upon denaturation. The distributions at intermediate urea concentrations could not be adequately described as a combination of native and denatured conformations, showing that CaM does not denature via a two-state process and demonstrating that at least one intermediate is present. The intermediate conformations formed upon addition of urea were different for Ca(2+)-CaM and apoCaM. An increase in the amplitude of a compact conformation in CaM was observed for apoCaM but not for Ca(2+)-CAM upon the addition of urea. The changes in the single-molecule distributions of CaM upon denaturation can be described by either a range of intermediate structures or by the presence of a single unfolding intermediate that grows in amplitude upon denaturation. A model for stepwise unfolding of CaM is suggested in which the domains of CaM unfold sequentially.
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Affiliation(s)
- Brian D Slaughter
- Department of Chemistry, 1251 Wescoe Hall Drive, University of Kansas, Lawrence, Kansas 66045-7582, USA
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