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Colombo J, Antkowiak A, Kogan K, Kotila T, Elliott J, Guillotin A, Lappalainen P, Michelot A. A functional family of fluorescent nucleotide analogues to investigate actin dynamics and energetics. Nat Commun 2021; 12:548. [PMID: 33483497 PMCID: PMC7822861 DOI: 10.1038/s41467-020-20827-4] [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: 05/08/2020] [Accepted: 12/15/2020] [Indexed: 01/30/2023] Open
Abstract
Actin polymerization provides force for vital processes of the eukaryotic cell, but our understanding of actin dynamics and energetics remains limited due to the lack of high-quality probes. Most current probes affect dynamics of actin or its interactions with actin-binding proteins (ABPs), and cannot track the bound nucleotide. Here, we identify a family of highly sensitive fluorescent nucleotide analogues structurally compatible with actin. We demonstrate that these fluorescent nucleotides bind to actin, maintain functional interactions with a number of essential ABPs, are hydrolyzed within actin filaments, and provide energy to power actin-based processes. These probes also enable monitoring actin assembly and nucleotide exchange with single-molecule microscopy and fluorescence anisotropy kinetics, therefore providing robust and highly versatile tools to study actin dynamics and functions of ABPs.
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Affiliation(s)
- Jessica Colombo
- grid.462081.90000 0004 0598 4854Aix Marseille Univ, CNRS, IBDM, Turing Centre for Living Systems, 13288 Marseille, France
| | - Adrien Antkowiak
- grid.462081.90000 0004 0598 4854Aix Marseille Univ, CNRS, IBDM, Turing Centre for Living Systems, 13288 Marseille, France
| | - Konstantin Kogan
- grid.7737.40000 0004 0410 2071HiLIFE Institute of Biotechnology, P.O. Box 56, University of Helsinki, 00014 Helsinki, Finland
| | - Tommi Kotila
- grid.7737.40000 0004 0410 2071HiLIFE Institute of Biotechnology, P.O. Box 56, University of Helsinki, 00014 Helsinki, Finland
| | - Jenna Elliott
- grid.462081.90000 0004 0598 4854Aix Marseille Univ, CNRS, IBDM, Turing Centre for Living Systems, 13288 Marseille, France
| | - Audrey Guillotin
- grid.462081.90000 0004 0598 4854Aix Marseille Univ, CNRS, IBDM, Turing Centre for Living Systems, 13288 Marseille, France
| | - Pekka Lappalainen
- grid.7737.40000 0004 0410 2071HiLIFE Institute of Biotechnology, P.O. Box 56, University of Helsinki, 00014 Helsinki, Finland
| | - Alphée Michelot
- grid.462081.90000 0004 0598 4854Aix Marseille Univ, CNRS, IBDM, Turing Centre for Living Systems, 13288 Marseille, France
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Nakayama H, Yamaga T. Visualization of F-actin filaments by a fluorescently labeled nucleotide analogue. Biophys Chem 1998; 75:1-6. [PMID: 9810684 DOI: 10.1016/s0301-4622(98)00194-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The tightly-bound nucleotide of F-actin was replaced with 1,N6-etheno-adenosine ATP (ADP). An epi-fluorescence optical microscope was modified to visualize efficiently the fluorescent analogue with an excitation-maximum wavelength of 310 nm. This microscope permitted us to visualize single F-actin filaments in solution using the fluorescence of the strongly bound 1,N6-ethenoadenosine nucleotide. Exchange of the tightly-bound nucleotide of F-actin with a free nucleotide in solution at a high temperature was quantitatively estimated by this method, and the results showed good agreement with results from phosphate release measurements.
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Affiliation(s)
- H Nakayama
- Kansai Advanced Research Center, Communications Research Laboratory, Kobe, Japan.
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3
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Nucleotide binding to actin. Cation dependence of nucleotide dissociation and exchange rates. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)52929-x] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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4
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Root DD, Reisler E. The accessibility of etheno-nucleotides to collisional quenchers and the nucleotide cleft in G- and F-actin. Protein Sci 1992; 1:1014-22. [PMID: 1304380 PMCID: PMC2142168 DOI: 10.1002/pro.5560010807] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Recent publication of the atomic structure of G-actin (Kabsch, W., Mannherz, H. G., Suck, D., Pai, E. F., & Holmes, K. C., 1990, Nature 347, 37-44) raises questions about how the conformation of actin changes upon its polymerization. In this work, the effects of various quenchers of etheno-nucleotides bound to G- and F-actin were examined in order to assess polymerization-related changes in the nucleotide phosphate site. The Mg(2+)-induced polymerization of actin quenched the fluorescence of the etheno-nucleotides by approximately 20% simultaneously with the increase in light scattering by actin. A conformational change at the nucleotide binding site was also indicated by greater accessibility of F-actin than G-actin to positively, negatively, and neutrally charged collisional quenchers. The difference in accessibility between G- and F-actin was greatest for I-, indicating that the environment of the etheno group is more positively charged in the polymerized form of actin. Based on calculations of the change in electric potential of the environment of the etheno group, specific polymerization-related movements of charged residues in the atomic structure of G-actin are suggested. The binding of S-1 to epsilon-ATP-G-actin increased the accessibility of the etheno group to I- even over that in Mg(2+)-polymerized actin. The quenching of the etheno group by nitromethane was, however, unaffected by the binding of S-1 to actin. Thus, the binding of S-1 induces conformational changes in the cleft region of actin that are different from those caused by Mg2+ polymerization of actin.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- D D Root
- Molecular Biology Institute, University of California, Los Angeles 90024
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5
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Abstract
Gelsolin, a Ca2+-modulated actin filament-capping and -severing protein, complexes with two actin monomers. Studies designed to localize binding sites on proteolytic fragments identify three distinct actin-binding peptides. 14NT, a 14-kD fragment that contains the NH2 terminal, will depolymerize F-actin. This peptide forms a 1:1 complex with G-actin which blocks the exchange of etheno-ATP from bound actin. The estimated association and dissociation rates for this complex are 0.3 microM-1 s-1 and 1.35 x 10(-6) s-1 which gives a maximum calculated Kd = 4.5 x 10(-12) M. 26NT, the adjacent peptide on the NH2-terminal half of gelsolin, binds to both G- and F-actin. This fragment has little or no intrinsic severing activity and will bind to F-actin to nearly stoichiometric ratios. The interactions of 14NT and 26NT with actin are largely Ca2+ independent and one of these sites, probably 14NT, is the EGTA-stable site identified in the intact protein. 41CT, the COOH-terminal half of gelsolin, forms a rapidly reversible 1:1 complex with actin, Kd = 25 nM, that slows but does not block etheno-ATP exchange. This interaction is Ca2+ dependent and is the exchangeable site in the intact protein. One of these sites is hidden in the intact protein, but cleavage into half fragments exposes all three and removes the Ca2+ dependence of severing.
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Affiliation(s)
- J Bryan
- Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030
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Perkins WJ, Wells JA, Yount RG. Characterization of the properties of ethenoadenosine nucleotides bound or trapped at the active site of myosin subfragment 1. Biochemistry 1984; 23:3994-4002. [PMID: 6237680 DOI: 10.1021/bi00312a029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The fluorescent nucleotide analogue of ADP, 1,N6-ethenoadenosine diphosphate (epsilon ADP), has been used to probe the active site of myosin subfragment 1 (SF1). The Mg complex of ADP was shown to be trapped stoichiometrically at the active site by a variety of thiol cross-linking agents having sulfur to sulfur spanning lengths of 2-14 A. Previous studies [Wells, J. A., & Yount, R. G. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 4966-4970] had suggested ADP was trapped by direct closure of a postulated active site cleft by cross-linking two activity critical thiols, SH1 and SH2. This model was tested by measuring the polarization of trapped and reversibly bound epsilon ADP, the off-rate of trapped epsilon ADP, and the solute quencher accessibility of trapped epsilon ADP on SF1 modified with thiol cross-linking agents of different spanning lengths. The lack of correlation of all of these properties with the length of the cross-linking span suggests that trapping occurs by indirect stabilization of a conformation favoring bound nucleotides rather than by sterically preventing the release of nucleotide. Measurement of the fluorescent properties of epsilon ADP bound to SF1 vs. epsilon ADP free gave a 20% increase in emission intensity, a 7-nm blue shift in the emission maximum, and a 70% increase in the absorbance at the excitation wavelength (330 nm). Trapping of epsilon ADP by the thiol cross-linking agent p-phenylenedimaleimide gave a further 24% increase in emission intensity. This change was shown to be the result of an increase in absorbance of trapped epsilon ADP at 330 nm rather than an increase in the quantum yield.(ABSTRACT TRUNCATED AT 250 WORDS)
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Dos Remedios CG, Cooke R. Fluorescence energy transfer between probes on actin and probes on myosin. BIOCHIMICA ET BIOPHYSICA ACTA 1984; 788:193-205. [PMID: 6743667 DOI: 10.1016/0167-4838(84)90262-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The structural relationship between F-actin filaments and the biologically active fragments of myosin (either as myosin subfragment-1 or heavy meromyosin) has been investigated using the technique of fluorescence energy transfer. Donor and acceptor probes were used to obtain the following inter- and intramolecular distances. Energy transfer was measured: (1) from the SH1 groups of the myosin 'heads' to the nucleotide sites of F-actin (in the absence of free nucleotide); (2) from the SH1 groups of myosin to multiple probes on the surface of the actin filament; (3) from the nucleotide-binding sites of F-actin to the ATPase sites of myosin; (4) from the ATPase sites of myosin to the nucleotide-binding sites of F-actin; (5) from the SH1 sites of myosin to the nucleotide-binding sites of F-actin; and (6) from the Cys-373 residues of F-actin to the nucleotide binding sites of F-actin. We observed very little energy transfer between the probes on actin and the probes on myosin (10% or less) and we observed a large transfer between the actin Cys-373 and the actin nucleotide. These data strongly suggest that both the SH1 moiety and the ATPase site of myosin are located more than 6 nm from the actin sites. When these distances are combined with similar measurements by other authors and inserted into the most recent three-dimensional reconstruction of electron micrographs of the acto-subfragment-1 complex, it is apparent that the SH1 and the ATPase sites on myosin are not located adjacent to actin and are most probably located in the half of the myosin head that is distal from actin in the actomyosin complex.
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Cheung HC, Liu BM. Distance between nucleotide site and cysteine-373 of G-actin by resonance energy transfer measurements. J Muscle Res Cell Motil 1984; 5:65-80. [PMID: 6715528 DOI: 10.1007/bf00713152] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The distance between the nucleotide site and the reactive cysteine-373 of G-actin was determined from resonance energy transfer measurements by using 1,N6-ethenoadenosine triphosphate (epsilon ATP) as the donor and 4-[N-(iodoacetoxy)ethyl N methyl]amino 7 nitrobenz 2 oxa 1,3 diazole covalently attached to the sulphydryl group as acceptor. The quenching of the lifetime of bound donor in the presence of attached acceptor arose predominantly from transfer of excitation energy. The polarization spectrum of free epilson ATP in glycerol revealed that the minimum value of its fundamental anisotropy is 0.32 at 340 nm, indicating that the maximum value of the angle between the absorption and emission dipoles of the ethenoadenosine moiety is 21 degrees. The polarization result indicates that the bound nucleotide is depolarized and has considerable motional freedom. This motion is restricted and unlikely to be rapid or isotropic during the time interval of energy transfer. The attached acceptor is highly immobile, however. The range of the donor-acceptor distance is 24-45 A. This range was not affected by polymerization. In the absence of independent structural information it is not possible to assign a single value to the donor-acceptor separation.
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9
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Leonard NJ. Etheno-substituted nucleotides and coenzymes: fluorescence and biological activity. CRC CRITICAL REVIEWS IN BIOCHEMISTRY 1984; 15:125-99. [PMID: 6365449 DOI: 10.3109/10409238409102299] [Citation(s) in RCA: 130] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Houk TW, Ovnic M, Karipides S. pH and polymerization dependence of the site of labeling of actin by 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(20)81906-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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11
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Borovikov YS, Levitskii DI, Kirillina VP, Poglazov BF. Effect of Ca2+ binding to 5,5'-dithiobis(2-nitrobenzoic acid) light chains on conformational changes of F-actin caused by myosin subfragment-1. EUROPEAN JOURNAL OF BIOCHEMISTRY 1982; 125:343-7. [PMID: 7117236 DOI: 10.1111/j.1432-1033.1982.tb06689.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The fluorescent ADP analogue, 1:N6-ethenoadenosine 5'-diphosphate, was incorporated into F-actin in a myosin-free ghost single fibre. Polarized fluorescence measurements of tryptophan residues and 1:N6-ethenoadenosine 5'-diphosphate were performed under a microspectrophotometer to investigate the conformation of F-actin and the changes induced in it by myosin subfragment-1 with 5,5'-dithiobis(2-nitrobenzoic acid) light chains and without them. A relation was found between the conformational state of F-actin and the presence of 5,5'-dithiobis(2-nitrobenzoic acid) light chains. The conformational changes were shown to be controlled by Ca2+ in the presence of 5,5'-dithiobis(2-nitrobenzoic acid) light chains.
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12
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Highsmith S. The dynamics of myosin and actin in solution are compatible with the mechanical features of the cross-bridge hypothesis. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 639:31-9. [PMID: 7030396 DOI: 10.1016/0304-4173(81)90003-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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13
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Wang YL, Taylor DL. Exchange of 1,N6-etheno-ATP with actin-bound nucleotides as a tool for studying the steady-state exchange of subunits in F-actin solutions. Proc Natl Acad Sci U S A 1981; 78:5503-7. [PMID: 6946487 PMCID: PMC348774 DOI: 10.1073/pnas.78.9.5503] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The fluorescent analog of ATP 1-N6-ethenoadenosine 5'-triphosphate (epsilon-ATP) exchanges readily with nucleotides bound to G-actin. The exchange can be observed by measuring the fluorescence intensity, which increases significantly when epsilon-ATP binds to actin. When excess epsilon-ATP is added to a solution of F-actin, a continuous increase in fluorescence intensity is observed, indicating that the nucleotides bound to F-actin are directly or indirectly exchangeable. The kinetics of exchange consist of a fast phase and a slow phase. Both phases are stimulated by shearing and are inhibited by phalloidin treatment, suggesting that the exchange of nucleotides is coupled to the exchange of subunits. Therefore, the exchange reaction can be used as a convenient, nonperturbing tool to study the exchange of free actin subunits with subunits in actin filaments. The exchange of actin subunits was characterized by a pulse-chase experiment. The results suggest that actin subunits assemble and disassemble through the same end of the filament during the fast phase of exchange but through opposite ends of the filament during the slow phase. In addition, the slow phase of exchange is inhibited in the absence of millimolar magnesium ions, but is not significantly affected by cytochalasin B at concentrations between 0.1 and 10 microM. These observations are discussed in relation to possible mechanisms of subunit exchange in steady-state F-actin solutions.
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15
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Neidl C, Engel J. Exchange of ADP, ATP and 1: N6-ethenoadenosine 5'-triphosphate at G-actin. Equilibrium and kinetics. EUROPEAN JOURNAL OF BIOCHEMISTRY 1979; 101:163-9. [PMID: 510301 DOI: 10.1111/j.1432-1033.1979.tb04228.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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16
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Kuramochi T, Inoue Y, Imakubo K. FLUORESCENCE NATURE OF PROTONATED 1, N6-ETHENOADENOSINE AND RELATED QUATERNIZED DERIVATIVES AT 293 AND 77°K. CHEM LETT 1979. [DOI: 10.1246/cl.1979.115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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17
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Burtnick LD, Schaar PL. Circular polarization of the fluorescence of actin-bound epsilon ATP Effects of binding DNase I. FEBS Lett 1979; 97:166-70. [PMID: 761614 DOI: 10.1016/0014-5793(79)80076-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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18
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Yanagida T, Oosawa F. Polarized fluorescence from epsilon-ADP incorporated into F-actin in a myosin-free single fiber: conformation of F-actin and changes induced in it by heavy meromyosin. J Mol Biol 1978; 126:507-24. [PMID: 370406 DOI: 10.1016/0022-2836(78)90056-6] [Citation(s) in RCA: 119] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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19
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Tao T. Nanosecond fluorescence depolarization studies on actin labeled with 1,5-IAEDANS and dansyl chloride. Evidence for label flexibility. FEBS Lett 1978; 93:146-50. [PMID: 700109 DOI: 10.1016/0014-5793(78)80824-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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20
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Miki M, Mihashi K. Fluorescence energy transfer between epsilon-ATP at the nucleotide binding site and N-(4-dimethylamino-3,5-dinitrophenyl)-maleimide at Cys-373 of G-actin. BIOCHIMICA ET BIOPHYSICA ACTA 1978; 533:163-72. [PMID: 638187 DOI: 10.1016/0005-2795(78)90560-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The method of fluorescence energy transfer is used to measure the distance from the nucleotide binding site to Cys-373 of G-actin. The fluorescent ATP analogue 1-N6-ethenoadenosine 5'-triphosphate was used as donor and N-(4-dimethylamino-3,5-dinitrophenyl)-maleimide was used as acceptor. From the measurements of the efficiency of fluorescence energy transfer by both static and time resolved fluorometries, the distance between nucleotide binding site and Cys-373 residue of G-actin was calculated to be about 30 A.
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21
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Engel J, Fasold H, Hulla FW, Waechter F, Wegner A. The polymerization reaction of muscle actin. Mol Cell Biochem 1977; 18:3-13. [PMID: 340937 DOI: 10.1007/bf00215273] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent advances in the studies of the aggregation of G-actin monomers, containing one molecule of ATP, to long filaments of F-actin, with a concomitant hydrolysis of the nucleotide to ADP, are reviewed. With the aid of omega-ATP, the association and dissociation rate constant of the nucleotide could be determined. The binding of the nucleotide is enhanced by the binding of one Ca++ ion, probably at a different site. The delta G value of the Mg++ or Ca++ induced polymerization has been determined to --39 to--59 kJ/mole, the critical protein concentration for the ATP-G-actin to ADP-F-actin conversion is very strongly influenced by the concentration of bivalent cations. The rate constants of the protein monomers, and the rate and equilibrium constants for the propagation step show the process to be extremely cooperative. Actin shows the interesting phenomenon of translocational head-to-tail polymerization, which may be regulated by ATP. The contact sites between the monomers in F-actin have been labeled by chemical modification. Two tryosine residues, 53 and 69, are probably close to one of the two sites. The ATP binding sites has been labeled by an ATP analog, and there is evidence that it is close to the contact site.
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22
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Waechter F, Engel J. Association kinetics and binding constants of nucleoside triphosphates with G-actin. EUROPEAN JOURNAL OF BIOCHEMISTRY 1977; 74:227-32. [PMID: 404146 DOI: 10.1111/j.1432-1033.1977.tb11385.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The dissociation of the complex between 1:N6-ethenoadenosine, 5'-triphosphate (xiATP) and G-actin was initiated by dilution to concentrations between 1 micronM and 5 nM and monitored by the fluorescence change of xiATP. The results were quantitatively explained by a two-step mechanism: a reversible dissociation of the actin-nucleotide complex followed by a fast irreversible inactivation of nucleotide-free G-actin. Under normal conditions (0.8 mM CaCl2, pH 8.2,21 degrees C), the rate-limiting step was the dissociation of the nucleotide-G-actin complex. The half-time of the dissociation of xiATP from G-actin was 290 s as compared to only 13 s for the following denaturation step of nucleotide-free actin. 1 mM EDTA highly accelerated the dissociation step and, regardless of its concentration, the complex dissociated quantitatively within 1 min. Addition of Ca2+ within 20 s after EDTA addition induced a re-association of xiATP with nucleotide-free but still native G-actin. This reversal was kinetically resolved by means of a multimixing stopped-flow apparatus. The association rate constant was 6 X 10(6) M-1s-1. From the association and dissociation rate constant, a value of 2.5 X (10(9) M-1 was calculated for the binding constant of xiATP to G-actin. The binding constant of ATP (1.4 X 10(10) M-1) was derived from the relative binding constant of xiATP and ATP as determined by fluorescence titration of xiATP-G-actin with ATP. These binding constants are 10(3)-10(4) times higher than values reported earlier on the basis of more indirect data.
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23
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Harvey SC, Cheung HC, Thames KE. Cooperativity in F-actin filaments on binding of myosin subfragments, demonstrated by fluorescence of 1, N6- ethenoadenosine diphosphate. Arch Biochem Biophys 1977; 179:391-6. [PMID: 322615 DOI: 10.1016/0003-9861(77)90126-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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24
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Harvey SC, Cheung HC. Fluorescence studies of 1,N6-ethenoadenosine triphosphate bound to G-actin: The nucleotide base is inaccessible to water. Biochem Biophys Res Commun 1976; 73:865-8. [PMID: 15625854 DOI: 10.1016/0006-291x(76)90201-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
When 1,N6-ethenoadenosine triphosphate (epsilon-ATP) is free in solution, its fluorescence is collisionally quenched by iodide ion, by methionine, by tryptophan, and by cysteine. None of these quenches the fluorescence of epsilon-ATP bound to G-actin. Thus, the ethenoadenine base is bound in a region of the protein which is inaccessible to collisions with these reagents. Since we have previously shown that the fluorescence of epsilon-ATP is quenched by water, the long lifetime of epsilon-ATP bound to G-actin (36 nsec, vs 27 nsec for epsilon-ATP in water) indicates that the bound nucleotide base is inaccessible to collisional quenching by water molecules.
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Affiliation(s)
- S C Harvey
- Biophysics Section, Department of Biomathematics, University of Alabama in Birmingham 35294, Birmingham, Alabama, USA
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26
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Abstract
At even the simplest level we can expect an ATPase mechanism to comprise the following four steps: the binding of ATP, the reaction of ATP with water on the enzyme, and the release of the products ADP and P1. So at the outset techniques are needed to investigate these four processes. The range of techniques needed is soon extended once questions are asked about the role of protons and metal ions, the possibility of a multistep hydrolytic process, multistep substrate and product binding processes, and protein–lipid or protein–protein interactions. Since ATPases and ATP synthases are almost universally involved in some form of energy transduction there is a particular need in an ATPase or ATP synthase reaction to evaluate the equilibrium constants of the steps in the mechanism and to investigate the possibility of alternate reaction pathways. The nature of the coupling process by the protein of the chemical reactions of ATP to the other energetic process, be it muscle contraction, active transport, respiration or photosynthesis, is likewise of profound interest. Finally we would like to know as much as possible about the ATPase or ATP synthase mechanism during the period when the various forms of energy transduction are occurring.
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27
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Mannherz HG, Brehme H, Lamp U. Depolymerisation of F-actin to G-actin and its repolymerisation in the presence of analogs of adenosine triphosphate. EUROPEAN JOURNAL OF BIOCHEMISTRY 1975; 60:109-16. [PMID: 128458 DOI: 10.1111/j.1432-1033.1975.tb20981.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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28
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Waechter F, Engel J. The kinetics of the exchange of G-actin-bound 1: N6-ethenoadenosine 5'-triphosphate with ATP as followed by fluorescence. EUROPEAN JOURNAL OF BIOCHEMISTRY 1975; 57:453-9. [PMID: 240724 DOI: 10.1111/j.1432-1033.1975.tb02320.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
1: N6-Ethenoadenosine 5'-triphosphate (epsilonATP), a fluorescent analog of ATP, binds to monomeric actin with a binding constant which is only about 5 times smaller than that of ATP. The spectroscopic changes which occur when epsilonATP binds to actin are studied and used to monitor the kinetics of nucleotide exchange. The first-order rate constant which is measured at a large excess of ATP over epsilonATP strongly depends on the ATP and Ca+ concentrations. This finding is explained by a mechanism in which the nucleotide dissociates much more easily from Ca2+-free than from Ca2+-bound actin. Of special interest is the temperature dependence of the dissociation rate constant. The Arrhenius plot shows a sharp bend near 24 degrees C.
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