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Pedersen RT, Snoberger A, Pyrpassopoulos S, Safer D, Drubin DG, Ostap EM. Endocytic myosin-1 is a force-insensitive, power-generating motor. J Cell Biol 2023; 222:e202303095. [PMID: 37549220 PMCID: PMC10406613 DOI: 10.1083/jcb.202303095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 05/17/2023] [Accepted: 07/24/2023] [Indexed: 08/09/2023] Open
Abstract
Myosins are required for clathrin-mediated endocytosis, but their precise molecular roles in this process are not known. This is, in part, because the biophysical properties of the relevant motors have not been investigated. Myosins have diverse mechanochemical activities, ranging from powerful contractility against mechanical loads to force-sensitive anchoring. To better understand the essential molecular contribution of myosin to endocytosis, we studied the in vitro force-dependent kinetics of the Saccharomyces cerevisiae endocytic type I myosin called Myo5, a motor whose role in clathrin-mediated endocytosis has been meticulously studied in vivo. We report that Myo5 is a low-duty-ratio motor that is activated ∼10-fold by phosphorylation and that its working stroke and actin-detachment kinetics are relatively force-insensitive. Strikingly, the in vitro mechanochemistry of Myo5 is more like that of cardiac myosin than that of slow anchoring myosin-1s found on endosomal membranes. We, therefore, propose that Myo5 generates power to augment actin assembly-based forces during endocytosis in cells.
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Affiliation(s)
- Ross T.A. Pedersen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Aaron Snoberger
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Serapion Pyrpassopoulos
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Daniel Safer
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - David G. Drubin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - E. Michael Ostap
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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2
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Pedersen RTA, Snoberger A, Pyrpassopoulos S, Safer D, Drubin DG, Ostap EM. Endocytic myosin-1 is a force-insensitive, power-generating motor. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.21.533689. [PMID: 36993306 PMCID: PMC10055380 DOI: 10.1101/2023.03.21.533689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Myosins are required for clathrin-mediated endocytosis, but their precise molecular roles in this process are not known. This is, in part, because the biophysical properties of the relevant motors have not been investigated. Myosins have diverse mechanochemical activities, ranging from powerful contractility against mechanical loads to force-sensitive anchoring. To better understand the essential molecular contribution of myosin to endocytosis, we studied the in vitro force-dependent kinetics of the Saccharomyces cerevisiae endocytic type I myosin called Myo5, a motor whose role in clathrin-mediated endocytosis has been meticulously studied in vivo. We report that Myo5 is a low-duty-ratio motor that is activated ∼10-fold by phosphorylation, and that its working stroke and actin-detachment kinetics are relatively force-insensitive. Strikingly, the in vitro mechanochemistry of Myo5 is more like that of cardiac myosin than like that of slow anchoring myosin-1s found on endosomal membranes. We therefore propose that Myo5 generates power to augment actin assembly-based forces during endocytosis in cells. Summary Pedersen, Snoberger et al. measure the force-sensitivity of the yeast endocytic the myosin-1 called Myo5 and find that it is more likely to generate power than to serve as a force-sensitive anchor in cells. Implications for Myo5's role in clathrin-mediated endocytosis are discussed.
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Affiliation(s)
- Ross TA Pedersen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
- Present address: Department of Embryology, Carnegie Institution for Science, Baltimore, MD 21218
- Equal Contribution
| | - Aaron Snoberger
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
- Equal Contribution
| | - Serapion Pyrpassopoulos
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Daniel Safer
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - David G Drubin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - E Michael Ostap
- Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
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3
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Clippinger Schulte SR, Scott B, Barrick SK, Stump WT, Blackwell T, Greenberg MJ. Single-molecule mechanics and kinetics of cardiac myosin interacting with regulated thin filaments. Biophys J 2023; 122:2544-2555. [PMID: 37165621 PMCID: PMC10323011 DOI: 10.1016/j.bpj.2023.05.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 04/18/2023] [Accepted: 05/05/2023] [Indexed: 05/12/2023] Open
Abstract
The cardiac cycle is a tightly regulated process wherein the heart generates force to pump blood to the body during systole and then relaxes during diastole. Disruption of this finely tuned cycle can lead to a range of diseases including cardiomyopathies and heart failure. Cardiac contraction is driven by the molecular motor myosin, which pulls regulated thin filaments in a calcium-dependent manner. In some muscle and nonmuscle myosins, regulatory proteins on actin tune the kinetics, mechanics, and load dependence of the myosin working stroke; however, it is not well understood whether or how thin-filament regulatory proteins tune the mechanics of the cardiac myosin motor. To address this critical gap in knowledge, we used single-molecule techniques to measure the kinetics and mechanics of the substeps of the cardiac myosin working stroke in the presence and absence of thin filament regulatory proteins. We found that regulatory proteins gate the calcium-dependent interactions between myosin and the thin filament. At physiologically relevant ATP concentrations, cardiac myosin's mechanics and unloaded kinetics are not affected by thin-filament regulatory proteins. We also measured the load-dependent kinetics of cardiac myosin at physiologically relevant ATP concentrations using an isometric optical clamp, and we found that thin-filament regulatory proteins do not affect either the identity or magnitude of myosin's primary load-dependent transition. Interestingly, at low ATP concentrations at both saturating and physiologically relevant subsaturating calcium concentrations, thin-filament regulatory proteins have a small effect on actomyosin dissociation kinetics, suggesting a mechanism beyond simple steric blocking. These results have important implications for the modeling of cardiac physiology and diseases.
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Affiliation(s)
- Sarah R Clippinger Schulte
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Brent Scott
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Samantha K Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - W Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Thomas Blackwell
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri.
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4
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Lee LA, Barrick SK, Buvoli AE, Walklate J, Stump WT, Geeves M, Greenberg MJ, Leinwand LA. Distinct effects of two hearing loss-associated mutations in the sarcomeric myosin MYH7b. J Biol Chem 2023; 299:104631. [PMID: 36963494 PMCID: PMC10141508 DOI: 10.1016/j.jbc.2023.104631] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 03/08/2023] [Accepted: 03/17/2023] [Indexed: 03/26/2023] Open
Abstract
For decades, sarcomeric myosin heavy chain proteins were assumed to be restricted to striated muscle where they function as molecular motors that contract muscle. However, MYH7b, an evolutionarily ancient member of this myosin family, has been detected in mammalian nonmuscle tissues, and mutations in MYH7b are linked to hereditary hearing loss in compound heterozygous patients. These mutations are the first associated with hearing loss rather than a muscle pathology, and because there are no homologous mutations in other myosin isoforms, their functional effects were unknown. We generated recombinant human MYH7b harboring the D515N or R1651Q hearing loss-associated mutation and studied their effects on motor activity and structural and assembly properties, respectively. The D515N mutation had no effect on steady-state actin-activated ATPase rate or load-dependent detachment kinetics but increased actin sliding velocity because of an increased displacement during the myosin working stroke. Furthermore, we found that the D515N mutation caused an increase in the proportion of myosin heads that occupy the disordered-relaxed state, meaning more myosin heads are available to interact with actin. Although we found no impact of the R1651Q mutation on myosin rod secondary structure or solubility, we observed a striking aggregation phenotype when this mutation was introduced into nonmuscle cells. Our results suggest that each mutation independently affects MYH7b function and structure. Together, these results provide the foundation for further study of a role for MYH7b outside the sarcomere.
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Affiliation(s)
- Lindsey A Lee
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA; BioFrontiers Institute, Boulder, Colorado, USA
| | - Samantha K Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Ada E Buvoli
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA; BioFrontiers Institute, Boulder, Colorado, USA
| | - Jonathan Walklate
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - W Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Michael Geeves
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Michael J Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Leslie A Leinwand
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA; BioFrontiers Institute, Boulder, Colorado, USA.
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Clippinger Schulte SR, Scott B, Barrick SK, Stump WT, Blackwell T, Greenberg MJ. Single Molecule Mechanics and Kinetics of Cardiac Myosin Interacting with Regulated Thin Filaments. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.09.522880. [PMID: 36711892 PMCID: PMC9881944 DOI: 10.1101/2023.01.09.522880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The cardiac cycle is a tightly regulated process wherein the heart generates force to pump blood to the body during systole and then relaxes during diastole. Disruption of this finely tuned cycle can lead to a range of diseases including cardiomyopathies and heart failure. Cardiac contraction is driven by the molecular motor myosin, which pulls regulated thin filaments in a calcium-dependent manner. In some muscle and non-muscle myosins, regulatory proteins on actin tune the kinetics, mechanics, and load dependence of the myosin working stroke; however, it is not well understood whether or how thin filament regulatory proteins tune the mechanics of the cardiac myosin motor. To address this critical gap in knowledge, we used single-molecule techniques to measure the kinetics and mechanics of the substeps of the cardiac myosin working stroke in the presence and absence of thin filament regulatory proteins. We found that regulatory proteins gate the calcium-dependent interactions between myosin and the thin filament. At physiologically relevant ATP concentrations, cardiac myosin's mechanics and unloaded kinetics are not affected by thin filament regulatory proteins. We also measured the load-dependent kinetics of cardiac myosin at physiologically relevant ATP concentrations using an isometric optical clamp, and we found that thin filament regulatory proteins do not affect either the identity or magnitude of myosin's primary load-dependent transition. Interestingly, at low ATP concentrations, thin filament regulatory proteins have a small effect on actomyosin dissociation kinetics, suggesting a mechanism beyond simple steric blocking. These results have important implications for both disease modeling and computational models of muscle contraction. Significance Statement Human heart contraction is powered by the molecular motor β-cardiac myosin, which pulls on thin filaments consisting of actin and the regulatory proteins troponin and tropomyosin. In some muscle and non-muscle systems, these regulatory proteins tune the kinetics, mechanics, and load dependence of the myosin working stroke. Despite having a central role in health and disease, it is not well understood whether the mechanics or kinetics of β-cardiac myosin are affected by regulatory proteins. We show that regulatory proteins do not affect the mechanics or load-dependent kinetics of the working stroke at physiologically relevant ATP concentrations; however, they can affect the kinetics at low ATP concentrations, suggesting a mechanism beyond simple steric blocking. This has important implications for modeling of cardiac physiology and diseases.
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Lee LA, Barrick SK, Meller A, Walklate J, Lotthammer JM, Tay JW, Stump WT, Bowman G, Geeves MA, Greenberg MJ, Leinwand LA. Functional divergence of the sarcomeric myosin, MYH7b, supports species-specific biological roles. J Biol Chem 2022; 299:102657. [PMID: 36334627 PMCID: PMC9800208 DOI: 10.1016/j.jbc.2022.102657] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 10/14/2022] [Accepted: 10/27/2022] [Indexed: 11/11/2022] Open
Abstract
Myosin heavy chain 7b (MYH7b) is an evolutionarily ancient member of the sarcomeric myosin family, which typically supports striated muscle function. However, in mammals, alternative splicing prevents MYH7b protein production in cardiac and most skeletal muscles and limits expression to a subset of specialized muscles and certain nonmuscle environments. In contrast, MYH7b protein is abundant in python cardiac and skeletal muscles. Although the MYH7b expression pattern diverges in mammals versus reptiles, MYH7b shares high sequence identity across species. So, it remains unclear how mammalian MYH7b function may differ from that of other sarcomeric myosins and whether human and python MYH7b motor functions diverge as their expression patterns suggest. Thus, we generated recombinant human and python MYH7b protein and measured their motor properties to investigate any species-specific differences in activity. Our results reveal that despite having similar working strokes, the MYH7b isoforms have slower actin-activated ATPase cycles and actin sliding velocities than human cardiac β-MyHC. Furthermore, python MYH7b is tuned to have slower motor activity than human MYH7b because of slower kinetics of the chemomechanical cycle. We found that the MYH7b isoforms adopt a higher proportion of myosin heads in the ultraslow, super-relaxed state compared with human cardiac β-MyHC. These findings are supported by molecular dynamics simulations that predict MYH7b preferentially occupies myosin active site conformations similar to those observed in the structurally inactive state. Together, these results suggest that MYH7b is specialized for slow and energy-conserving motor activity and that differential tuning of MYH7b orthologs contributes to species-specific biological roles.
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Affiliation(s)
- Lindsey A. Lee
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA,BioFrontiers Institute, University of Colorado Boulder, Boulder, Colorado, USA
| | - Samantha K. Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Artur Meller
- The Center for Science and Engineering of Living Systems, Washington University in St Louis, St Louis, Missouri, USA
| | - Jonathan Walklate
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Jeffrey M. Lotthammer
- The Center for Science and Engineering of Living Systems, Washington University in St Louis, St Louis, Missouri, USA
| | - Jian Wei Tay
- BioFrontiers Institute, University of Colorado Boulder, Boulder, Colorado, USA
| | - W. Tom Stump
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Gregory Bowman
- The Center for Science and Engineering of Living Systems, Washington University in St Louis, St Louis, Missouri, USA,Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Michael A. Geeves
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Michael J. Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, Missouri, USA
| | - Leslie A. Leinwand
- Molecular, Cellular, and Developmental Biology Department, Boulder, Colorado, USA,BioFrontiers Institute, University of Colorado Boulder, Boulder, Colorado, USA,For correspondence: Leslie A. Leinwand
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Wang T, Spahiu E, Osten J, Behrens F, Grünhagen F, Scholz T, Kraft T, Nayak A, Amrute-Nayak M. Cardiac ventricular myosin and slow skeletal myosin exhibit dissimilar chemomechanical properties despite bearing the same myosin heavy chain isoform. J Biol Chem 2022; 298:102070. [PMID: 35623390 PMCID: PMC9243179 DOI: 10.1016/j.jbc.2022.102070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Revised: 05/12/2022] [Accepted: 05/14/2022] [Indexed: 11/29/2022] Open
Abstract
The myosin II motors are ATP-powered force-generating machines driving cardiac and muscle contraction. Myosin II heavy chain isoform-beta (β-MyHC) is primarily expressed in the ventricular myocardium and in slow-twitch muscle fibers, such as M. soleus. M. soleus–derived myosin II (SolM-II) is often used as an alternative to the ventricular β-cardiac myosin (βM-II); however, the direct assessment of biochemical and mechanical features of the native myosins is limited. By employing optical trapping, we examined the mechanochemical properties of native myosins isolated from the rabbit heart ventricle and soleus muscles at the single-molecule level. We found purified motors from the two tissue sources, despite expressing the same MyHC isoform, displayed distinct motile and ATPase kinetic properties. We demonstrate βM-II was approximately threefold faster in the actin filament–gliding assay than SolM-II. The maximum actomyosin (AM) detachment rate derived in single-molecule assays was also approximately threefold higher in βM-II, while the power stroke size and stiffness of the “AM rigor” crossbridge for both myosins were comparable. Our analysis revealed a higher AM detachment rate for βM-II, corresponding to the enhanced ADP release rates from the crossbridge, likely responsible for the observed differences in the motility driven by these myosins. Finally, we observed a distinct myosin light chain 1 isoform (MLC1sa) that associates with SolM-II, which might contribute to the observed kinetics differences between βM-II and SolM-II. These results have important implications for the choice of tissue sources and justify prerequisites for the correct myosin heavy and light chains to study cardiomyopathies.
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Affiliation(s)
- Tianbang Wang
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Emrulla Spahiu
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Jennifer Osten
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Florentine Behrens
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Fabius Grünhagen
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Tim Scholz
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Theresia Kraft
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Arnab Nayak
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany.
| | - Mamta Amrute-Nayak
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany.
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Scott B, Marang C, Woodward M, Debold EP. Myosin's powerstroke occurs prior to the release of phosphate from the active site. Cytoskeleton (Hoboken) 2021; 78:185-198. [PMID: 34331410 DOI: 10.1002/cm.21682] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 07/15/2021] [Accepted: 07/19/2021] [Indexed: 02/06/2023]
Abstract
Myosins are a family of motor proteins responsible for various forms of cellular motility, including muscle contraction and vesicular transport. The most fundamental aspect of myosin is its ability to transduce the chemical energy from the hydrolysis of ATP into mechanical work, in the form of force and/or motion. A key unanswered question of the transduction process is the timing of the force-generating powerstroke relative to the release of phosphate (Pi ) from the active site. We examined the ability of single-headed myosin Va to generate a powerstroke in a single molecule laser trap assay while maintaining Pi in its active site, by either elevating Pi in solution or by introducing a mutation in myosin's active site (S217A) to slow Pi -release from the active site. Upon binding to the actin filament, WT myosin generated a powerstoke rapidly (≥500 s-1 ) and without a detectable delay, both in the absence and presence of 30 mM Pi . The elevated levels of Pi did, however, affect event lifetime, eliminating the longest 25% of binding events, confirming that Pi rebound to myosin's active site and accelerated detachment. The S217A construct also generated a powerstroke similar in size and rate upon binding to actin despite the slower Pi release rate. These findings provide direct evidence that myosin Va generates a powerstroke with Pi still in its active site. Therefore, the findings are most consistent with a model in which the powerstroke occurs prior to the release of Pi from the active site.
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Affiliation(s)
- Brent Scott
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts, USA
| | - Christopher Marang
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts, USA
| | - Mike Woodward
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts, USA
| | - Edward P Debold
- Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts, USA
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