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Stafford WF, Walker ML, Trinick JA, Coluccio LM. Mammalian class I myosin, Myo1b, is monomeric and cross-links actin filaments as determined by hydrodynamic studies and electron microscopy. Biophys J 2004; 88:384-91. [PMID: 15475577 PMCID: PMC1305015 DOI: 10.1529/biophysj.104.045245] [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: 11/18/2022] Open
Abstract
The class I myosin, Myo1b, is a calmodulin- and actin-associated molecular motor widely expressed in mammalian tissues. Analytical ultracentrifugation studies indicate that Myo1b purified from rat liver has a Stokes radius of 6.7 nm and a sedimentation coefficient, s(20,w), of 7.0 S with a predicted molar mass of 213 kg/mol. These results indicate that Myo1b is monomeric and consists primarily of a splice variant having five associated calmodulins. Molecular modeling based on the analytical ultracentrifugation studies are supported by electron microscopy studies that depict Myo1b as a single-headed, tadpole-shaped molecule with outer dimensions of 27.9 x 4.0 nm. Above a certain Myo1b/actin ratio, Myo1b bundles actin filaments presumably by virtue of a second actin-binding site. These studies provide new information regarding the oligomeric state and morphology of Myo1b and support a model in which Myo1b cross-links actin through a cryptic actin-binding site.
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Affiliation(s)
- Walter F. Stafford
- Boston Biomedical Research Institute, Watertown, Massachusetts; and Asbury Centre for Structural Molecular Biology and School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Matt L. Walker
- Boston Biomedical Research Institute, Watertown, Massachusetts; and Asbury Centre for Structural Molecular Biology and School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - John A. Trinick
- Boston Biomedical Research Institute, Watertown, Massachusetts; and Asbury Centre for Structural Molecular Biology and School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Lynne M. Coluccio
- Boston Biomedical Research Institute, Watertown, Massachusetts; and Asbury Centre for Structural Molecular Biology and School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
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52
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Risal D, Gourinath S, Himmel DM, Szent-Györgyi AG, Cohen C. Myosin subfragment 1 structures reveal a partially bound nucleotide and a complex salt bridge that helps couple nucleotide and actin binding. Proc Natl Acad Sci U S A 2004; 101:8930-5. [PMID: 15184651 PMCID: PMC428449 DOI: 10.1073/pnas.0403002101] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Structural studies of myosin have indicated some of the conformational changes that occur in this protein during the contractile cycle, and we have now observed a conformational change in a bound nucleotide as well. The 3.1-A x-ray structure of the scallop myosin head domain (subfragment 1) in the ADP-bound near-rigor state (lever arm =45 degrees to the helical actin axis) shows the diphosphate moiety positioned on the surface of the nucleotide-binding pocket, rather than deep within it as had been observed previously. This conformation strongly suggests a specific mode of entry and exit of the nucleotide from the nucleotide-binding pocket through the so-called "front door." In addition, using a variety of scallop structures, including a relatively high-resolution 2.75-A nucleotide-free near-rigor structure, we have identified a conserved complex salt bridge connecting the 50-kDa upper and N-terminal subdomains. This salt bridge is present only in crystal structures of muscle myosin isoforms that exhibit a strong reciprocal relationship (also known as coupling) between actin and nucleotide affinity.
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Affiliation(s)
- Dipesh Risal
- Rosenstiel Basic Medical Sciences Research Center, MS 029, Waltham, MA 02454-9110, USA
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53
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Abstract
Given their prominent actin-rich subcellular specializations, it is no surprise that mechanosensitive hair cells of the inner ear exploit myosin molecules-the only known actin-dependent molecular motors-to carry out exotic but essential tasks. Recent experiments have confirmed that an unconventional myosin isozyme, myosin-1c, is a component of the hair cell's adaptation-motor complex. This complex carries out slow adaptation, provides tension to sensitize transduction channels, and may participate in assembly of the transduction apparatus. This review focuses on the detailed operation of the adaptation motor and the functional consequences of the incorporation of this specific myosin isozyme into the motor complex.
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Affiliation(s)
- Peter G Gillespie
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239, USA.
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54
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Batters C, Arthur CP, Lin A, Porter J, Geeves MA, Milligan RA, Molloy JE, Coluccio LM. Myo1c is designed for the adaptation response in the inner ear. EMBO J 2004; 23:1433-40. [PMID: 15014434 PMCID: PMC391074 DOI: 10.1038/sj.emboj.7600169] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2003] [Accepted: 02/19/2004] [Indexed: 11/09/2022] Open
Abstract
The molecular motor, Myo1c, a member of the myosin family, is widely expressed in vertebrate tissues. Its presence at strategic places in the stereocilia of the hair cells in the inner ear and studies using transgenic mice expressing a mutant Myo1c that can be selectively inhibited implicate it as the mediator of slow adaptation of mechanoelectrical transduction, which is required for balance. Here, we have studied the structural, mechanical and biochemical properties of Myo1c to gain an insight into how this molecular motor works. Our results support a model in which Myo1c possesses a strain-sensing ADP-release mechanism, which allows it to adapt to mechanical load.
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Affiliation(s)
- Christopher Batters
- Division of Physical Biochemistry, National Institutes for Medical Research, The Ridgeway, Mill Hill, London, UK
| | - Christopher P Arthur
- Center for Integrative Molecular Biosciences, The Scripps Research Institute, La Jolla, CA, USA
| | - Abel Lin
- Center for Integrative Molecular Biosciences, The Scripps Research Institute, La Jolla, CA, USA
| | - Jessica Porter
- Boston Biomedical Research Institute, Watertown, MA, USA
| | - Michael A Geeves
- Department of Biosciences, University of Kent, Canterbury, Kent, UK
| | - Ronald A Milligan
- Center for Integrative Molecular Biosciences, The Scripps Research Institute, La Jolla, CA, USA
| | - Justin E Molloy
- Division of Physical Biochemistry, National Institutes for Medical Research, The Ridgeway, Mill Hill, London, UK
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55
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Abstract
Axonal transport in neurons has been shown to be microtubule dependent, driven by the molecular motor proteins kinesin and dynein. However, organelles undergoing fast transport can often pause or rapidly change directions without apparent dissociation from their transport tracks. Cytoskeletal polymers such as neurofilaments and microtubules have also been shown to make infrequent but rapid movements in axons indicating that their transport is likely to involve molecular motors. In addition, neurons have multiple compartments that are devoid of microtubules where transport of organelles is still seen to occur. These areas are rich in other cytoskeletal polymers such as actin filaments. Transported organelles have been shown to associate with multiple motor proteins including myosins. This suggests that nonmicrotubule-based transport may be myosin driven. In this review we will focus our attention on myosin motors known to be present in neurons and evaluate the evidence that they contribute to transport or other functions in the different compartments of the neuron.
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Affiliation(s)
- Paul C Bridgman
- Department of Anatomy and Neurobiology, Washington University School of Medicine, Box 8108, 660 S. Euclid Avenue, St. Louis, Missouri 63110, USA.
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56
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Abstract
All characterized myosins share a common ATPase mechanism. However, detailed kinetic analyses suggest that modulation of the rate and equilibrium constants that define the ATPase cycle confers specific properties to these motor proteins, suiting them to specific physiological tasks. Understanding the kinetic mechanisms allows potential cellular functions of the different myosin classes and isoforms to be better defined.
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Affiliation(s)
- Enrique M De La Cruz
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208114, New Haven, CT 06520, USA
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57
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Miller BM, Nyitrai M, Bernstein SI, Geeves MA. Kinetic analysis of Drosophila muscle myosin isoforms suggests a novel mode of mechanochemical coupling. J Biol Chem 2003; 278:50293-300. [PMID: 14506231 DOI: 10.1074/jbc.m308318200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The molecular mechanism of myosin function was addressed by measuring transient kinetic parameters of naturally occurring and chimeric Drosophila muscle myosin isoforms. We assessed the native embryonic isoform, the native indirect flight muscle isoform, and two chimeric isoforms containing converter domains exchanged between the indirect flight muscle and embryonic isoforms. Myosin was purified from the indirect flight muscles of transgenic flies, and S1 was produced by alpha-chymotryptic digestion. Previous studies in vertebrate and scallop myosins have shown a correlation between actin filament velocity in motility assays and cross-bridge detachment rate, specifically the rate of ADP release. In contrast, our study showed no correlation between the detachment rate and actin filament velocity in Drosophila myosin isoforms and further that the converter domain does not significantly influence the biochemical kinetics governing the detachment of myosin from actin. We suggest that evolutionary pressure on a single muscle myosin gene may maintain a fast detachment rate in all isoforms. As a result, the attachment rate and completion of the power stroke or the equilibrium between actin.myosin.ADP states may define actin filament velocity for these myosin isoforms.
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MESH Headings
- Actins/chemistry
- Adenosine Triphosphatases/chemistry
- Adenosine Triphosphate/chemistry
- Amino Acid Sequence
- Animals
- Animals, Genetically Modified
- Ca(2+) Mg(2+)-ATPase/chemistry
- Chymotrypsin/metabolism
- Dose-Response Relationship, Drug
- Drosophila melanogaster/metabolism
- Electrophoresis, Polyacrylamide Gel
- Kinetics
- Light
- Magnesium/chemistry
- Models, Chemical
- Models, Molecular
- Molecular Sequence Data
- Muscle, Skeletal/metabolism
- Muscles/metabolism
- Myosins/chemistry
- Myosins/metabolism
- Photolysis
- Protein Binding
- Protein Isoforms
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Rabbits
- Scattering, Radiation
- Sequence Homology, Amino Acid
- Time Factors
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Affiliation(s)
- Becky M Miller
- Department of Biology and Molecular Biology Institute, San Diego State University, San Diego, California 92182-4614, USA
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58
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Abstract
Members of the myosin II class of molecular motors have been referred to as "conventional," a term used to describe their ability to form thick filaments, their low duty ratio, the ability of individual motor-containing "heads" to operate independently of each other, and their rate-limiting phosphate release. These features ensure that those motors that have completed their power stroke dissociate rapidly enough to prevent them from interfering with those motors that are beginning theirs. However, in this study, we demonstrate that myosin IIB, a cytoplasmic myosin II particularly enriched in the central nervous system and cardiac tissue, has a number of features that it shares instead with "unconventional" myosin isoforms, including myosins V and VI. These include a high duty ratio, rate-limiting ADP release, and high ADP affinity. These features imply that myosin IIB serves a set of physiologic needs different from those served by its more conventional myosin II counterparts, and this work provides a plausible basis for explaining the physiologic role of this unconventionally conventional myosin.
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Affiliation(s)
- Steven S Rosenfeld
- Departments of Neurology and Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama 35294-3293, USA.
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59
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Abstract
Myosin VIIA was cloned from rat kidney, and the construct (M7IQ5) containing the motor domain, IQ domain, and the coiled-coil domain as well as the full-length myosin VIIA (M7full) was expressed. The M7IQ5 contained five calmodulins. Based upon native gel electrophoresis and gel filtration, it was found that M7IQ5 was single-headed, whereas M7full was two-headed, suggesting that the tail domain contributes to form the two-headed structure. M7IQ5 had Mg(2+)-ATPase activity that was markedly activated by actin with K(actin) of 33 microm and V(max) of 0.53 s(-1) head(-1). Myosin VIIA required an extremely high ATP concentration for ATPase activity, ATP-induced dissociation from actin, and in vitro actin-translocating activity. ADP markedly inhibited the actin-activated ATPase activity. ADP also significantly inhibited the ATP-induced dissociation of myosin VIIA from actin. Consistently, ADP decreased K(actin) of the actin-activated ATPase. ADP decreased the actin gliding velocity, although ADP did not stop the actin gliding even at high concentration. These results suggest that myosin VIIA has slow ATP binding or low affinity for ATP and relatively high affinity for ADP. The directionality of myosin VIIA was determined by using the polarity-marked dual fluorescence-labeled actin filaments. It was found that myosin VIIA is a plus-directed motor.
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Affiliation(s)
- Akira Inoue
- Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655-0127, USA
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60
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Rüegg C, Veigel C, Molloy JE, Schmitz S, Sparrow JC, Fink RHA. Molecular motors: force and movement generated by single myosin II molecules. Physiology (Bethesda) 2002; 17:213-8. [PMID: 12270959 DOI: 10.1152/nips.01389.2002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Muscle myosin II is an ATP-driven, actin-based molecular motor. Recent developments in optical tweezers technology have made it possible to study movement and force production on the single-molecule level and to find out how different myosin isoforms may have adapted to their specific physiological roles.
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Affiliation(s)
- Caspar Rüegg
- Department of Physiology and Pathophysiology, University of Heidelberg, INF 326, D-69126 Heidelberg, Germany
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61
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El Mezgueldi M, Tang N, Rosenfeld SS, Ostap EM. The kinetic mechanism of Myo1e (human myosin-IC). J Biol Chem 2002; 277:21514-21. [PMID: 11940582 DOI: 10.1074/jbc.m200713200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Myo1e is the widely expressed subclass-1 member of the myosin-I family. We performed a kinetic analysis of a truncated myo1e that consists of the motor and the single IQ motif with a bound calmodulin. We determined the rates and equilibrium constants for the key steps in the ATPase cycle. The maximum actin activated ATPase rate (V(max)) and the actin concentration at half-maximum of V(max) (K(ATPase)) of myo1e are similar to those of the native protein. The K(ATPase) is low (approximately 1 microm), however the affinity of myo1e for actin in the presence of ATP is very weak. A weak actin affinity and a rapid rate of phosphate release result in a pathway under in vitro assay conditions in which phosphate is released while myo1e is dissociated from actin. Actin activation of the ATPase activity and the low K(ATPase) are the result of actin activation of ADP release. We propose that myo1e is tuned to function in regions of high concentrations of cross-linked actin filaments. Additionally, we found that ADP release from actomyo1e is > 10-fold faster than other vertebrate myosin-I isoforms. We propose that subclass-1 myosin-Is are tuned for rapid sliding, whereas subclass-2 isoforms are tuned for tension maintenance or stress sensing.
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Affiliation(s)
- Mohammed El Mezgueldi
- Department of Physiology and The Pennsylvania Muscle Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6085, USA
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62
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Herm-Götz A, Weiss S, Stratmann R, Fujita-Becker S, Ruff C, Meyhöfer E, Soldati T, Manstein DJ, Geeves MA, Soldati D. Toxoplasma gondii myosin A and its light chain: a fast, single-headed, plus-end-directed motor. EMBO J 2002; 21:2149-58. [PMID: 11980712 PMCID: PMC125985 DOI: 10.1093/emboj/21.9.2149] [Citation(s) in RCA: 177] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2001] [Revised: 02/26/2002] [Accepted: 03/08/2002] [Indexed: 11/14/2022] Open
Abstract
Successful host cell invasion is a prerequisite for survival of the obligate intracellular apicomplexan parasites and establishment of infection. Toxoplasma gondii penetrates host cells by an active process involving its own actomyosin system and which is distinct from induced phagocytosis. Toxoplasma gondii myosin A (TgMyoA) is presumed to achieve power gliding motion and host cell penetration by the capping of apically released adhesins towards the rear of the parasite. We report here an extensive biochemical characterization of the functional TgMyoA motor complex. TgMyoA is anchored at the plasma membrane and binds a novel type of myosin light chain (TgMLC1). Despite some unusual features, the kinetic and mechanical properties of TgMyoA are unexpectedly similar to those of fast skeletal muscle myosins. Microneedle-laser trap and sliding velocity assays established that TgMyoA moves in unitary steps of 5.3 nm with a velocity of 5.2 microm/s towards the plus end of actin filaments. TgMyoA is the first fast, single-headed myosin and fulfils all the requirements for power parasite gliding.
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Affiliation(s)
- Angelika Herm-Götz
- Zentrum für Molekulare Biologie, Universität Heidelberg, Im Neuenheimer Feld 282, Department of Biophysics and Department of Molecular Cell Research, Max-Plank-Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Department of Molecular and Cellular Physiology, Medical School Hanover,Carl-Neuberg Strasse 1, D-30625 Hanover, Germany and Department of Biosciences, University of Kent, Canterbury CT2 7NJ, UK Present address: Department of Biological Sciences, Imperial College of Science, Technology and Medicine, Sir Alexander Fleming Building, Imperial College Road, London SW7 2AZ, UK Present address: Department of Mechanical Engineering, University of Michigan, 3130 G.G.Brown Building, 2350 Hayward Street, Ann Arbor, MI 48109-2125, USA Corresponding author e-mail:
| | - Stefan Weiss
- Zentrum für Molekulare Biologie, Universität Heidelberg, Im Neuenheimer Feld 282, Department of Biophysics and Department of Molecular Cell Research, Max-Plank-Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Department of Molecular and Cellular Physiology, Medical School Hanover,Carl-Neuberg Strasse 1, D-30625 Hanover, Germany and Department of Biosciences, University of Kent, Canterbury CT2 7NJ, UK Present address: Department of Biological Sciences, Imperial College of Science, Technology and Medicine, Sir Alexander Fleming Building, Imperial College Road, London SW7 2AZ, UK Present address: Department of Mechanical Engineering, University of Michigan, 3130 G.G.Brown Building, 2350 Hayward Street, Ann Arbor, MI 48109-2125, USA Corresponding author e-mail:
| | - Rolf Stratmann
- Zentrum für Molekulare Biologie, Universität Heidelberg, Im Neuenheimer Feld 282, Department of Biophysics and Department of Molecular Cell Research, Max-Plank-Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Department of Molecular and Cellular Physiology, Medical School Hanover,Carl-Neuberg Strasse 1, D-30625 Hanover, Germany and Department of Biosciences, University of Kent, Canterbury CT2 7NJ, UK Present address: Department of Biological Sciences, Imperial College of Science, Technology and Medicine, Sir Alexander Fleming Building, Imperial College Road, London SW7 2AZ, UK Present address: Department of Mechanical Engineering, University of Michigan, 3130 G.G.Brown Building, 2350 Hayward Street, Ann Arbor, MI 48109-2125, USA Corresponding author e-mail:
| | - Setsuko Fujita-Becker
- Zentrum für Molekulare Biologie, Universität Heidelberg, Im Neuenheimer Feld 282, Department of Biophysics and Department of Molecular Cell Research, Max-Plank-Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Department of Molecular and Cellular Physiology, Medical School Hanover,Carl-Neuberg Strasse 1, D-30625 Hanover, Germany and Department of Biosciences, University of Kent, Canterbury CT2 7NJ, UK Present address: Department of Biological Sciences, Imperial College of Science, Technology and Medicine, Sir Alexander Fleming Building, Imperial College Road, London SW7 2AZ, UK Present address: Department of Mechanical Engineering, University of Michigan, 3130 G.G.Brown Building, 2350 Hayward Street, Ann Arbor, MI 48109-2125, USA Corresponding author e-mail:
| | - Christine Ruff
- Zentrum für Molekulare Biologie, Universität Heidelberg, Im Neuenheimer Feld 282, Department of Biophysics and Department of Molecular Cell Research, Max-Plank-Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Department of Molecular and Cellular Physiology, Medical School Hanover,Carl-Neuberg Strasse 1, D-30625 Hanover, Germany and Department of Biosciences, University of Kent, Canterbury CT2 7NJ, UK Present address: Department of Biological Sciences, Imperial College of Science, Technology and Medicine, Sir Alexander Fleming Building, Imperial College Road, London SW7 2AZ, UK Present address: Department of Mechanical Engineering, University of Michigan, 3130 G.G.Brown Building, 2350 Hayward Street, Ann Arbor, MI 48109-2125, USA Corresponding author e-mail:
| | - Edgar Meyhöfer
- Zentrum für Molekulare Biologie, Universität Heidelberg, Im Neuenheimer Feld 282, Department of Biophysics and Department of Molecular Cell Research, Max-Plank-Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Department of Molecular and Cellular Physiology, Medical School Hanover,Carl-Neuberg Strasse 1, D-30625 Hanover, Germany and Department of Biosciences, University of Kent, Canterbury CT2 7NJ, UK Present address: Department of Biological Sciences, Imperial College of Science, Technology and Medicine, Sir Alexander Fleming Building, Imperial College Road, London SW7 2AZ, UK Present address: Department of Mechanical Engineering, University of Michigan, 3130 G.G.Brown Building, 2350 Hayward Street, Ann Arbor, MI 48109-2125, USA Corresponding author e-mail:
| | - Thierry Soldati
- Zentrum für Molekulare Biologie, Universität Heidelberg, Im Neuenheimer Feld 282, Department of Biophysics and Department of Molecular Cell Research, Max-Plank-Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Department of Molecular and Cellular Physiology, Medical School Hanover,Carl-Neuberg Strasse 1, D-30625 Hanover, Germany and Department of Biosciences, University of Kent, Canterbury CT2 7NJ, UK Present address: Department of Biological Sciences, Imperial College of Science, Technology and Medicine, Sir Alexander Fleming Building, Imperial College Road, London SW7 2AZ, UK Present address: Department of Mechanical Engineering, University of Michigan, 3130 G.G.Brown Building, 2350 Hayward Street, Ann Arbor, MI 48109-2125, USA Corresponding author e-mail:
| | - Dietmar J. Manstein
- Zentrum für Molekulare Biologie, Universität Heidelberg, Im Neuenheimer Feld 282, Department of Biophysics and Department of Molecular Cell Research, Max-Plank-Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Department of Molecular and Cellular Physiology, Medical School Hanover,Carl-Neuberg Strasse 1, D-30625 Hanover, Germany and Department of Biosciences, University of Kent, Canterbury CT2 7NJ, UK Present address: Department of Biological Sciences, Imperial College of Science, Technology and Medicine, Sir Alexander Fleming Building, Imperial College Road, London SW7 2AZ, UK Present address: Department of Mechanical Engineering, University of Michigan, 3130 G.G.Brown Building, 2350 Hayward Street, Ann Arbor, MI 48109-2125, USA Corresponding author e-mail:
| | - Michael A. Geeves
- Zentrum für Molekulare Biologie, Universität Heidelberg, Im Neuenheimer Feld 282, Department of Biophysics and Department of Molecular Cell Research, Max-Plank-Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Department of Molecular and Cellular Physiology, Medical School Hanover,Carl-Neuberg Strasse 1, D-30625 Hanover, Germany and Department of Biosciences, University of Kent, Canterbury CT2 7NJ, UK Present address: Department of Biological Sciences, Imperial College of Science, Technology and Medicine, Sir Alexander Fleming Building, Imperial College Road, London SW7 2AZ, UK Present address: Department of Mechanical Engineering, University of Michigan, 3130 G.G.Brown Building, 2350 Hayward Street, Ann Arbor, MI 48109-2125, USA Corresponding author e-mail:
| | - Dominique Soldati
- Zentrum für Molekulare Biologie, Universität Heidelberg, Im Neuenheimer Feld 282, Department of Biophysics and Department of Molecular Cell Research, Max-Plank-Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Department of Molecular and Cellular Physiology, Medical School Hanover,Carl-Neuberg Strasse 1, D-30625 Hanover, Germany and Department of Biosciences, University of Kent, Canterbury CT2 7NJ, UK Present address: Department of Biological Sciences, Imperial College of Science, Technology and Medicine, Sir Alexander Fleming Building, Imperial College Road, London SW7 2AZ, UK Present address: Department of Mechanical Engineering, University of Michigan, 3130 G.G.Brown Building, 2350 Hayward Street, Ann Arbor, MI 48109-2125, USA Corresponding author e-mail:
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63
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Abstract
The kidney epithelial cell line, LLC-PK1-CL4 (CL4), forms a well ordered brush border (BB) on its apical surface. CL4 cells were used to examine the dynamics of MYO1A (M1A; formerly BB myosin I) within the BB using GFP-tagged MIA (GFP-M1A), MIA motor domain (GFP-MDIQ), and tail domain (GFP-Tail). GFP-beta-actin (GFP-Actin) was used to assess actin dynamics within the BB. GFP-M1A, GFP-Tail, but not GFP-MDIQ localized to the BB, indicating that the tail is sufficient for apical targeting of M1A. GFP-Actin targeted to all the actin domains of the cell including the BB. Fluorescence recovery after photobleaching analysis revealed that GFP-M1A and GFP-Tail turnover in the BB is rapid, approximately 80% complete in <1 min. As expected for an actin-based motor, ATP depletion resulted in significant inhibition of GFP-M1A turnover yet had little effect on GFP-Tail exchange. Rapid turnover of GFP-M1A and GFP-Tail was not due to actin turnover as GFP-Actin turnover in the BB was much slower. These results indicate that the BB population of M1A turns over rapidly, while its head and tail domains interact transiently with the core actin and plasma membrane, respectively. This rapidly exchanging pool of M1A envelops an actin core bundle that, by comparison, is static in structure.
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Affiliation(s)
- M J Tyska
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520, USA. matthew.tyska.@yale.edu
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64
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Cordonnier MN, Dauzonne D, Louvard D, Coudrier E. Actin filaments and myosin I alpha cooperate with microtubules for the movement of lysosomes. Mol Biol Cell 2001; 12:4013-29. [PMID: 11739797 PMCID: PMC60772 DOI: 10.1091/mbc.12.12.4013] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
An earlier report suggested that actin and myosin I alpha (MMIalpha), a myosin associated with endosomes and lysosomes, were involved in the delivery of internalized molecules to lysosomes. To determine whether actin and MMIalpha were involved in the movement of lysosomes, we analyzed by time-lapse video microscopy the dynamic of lysosomes in living mouse hepatoma cells (BWTG3 cells), producing green fluorescent protein actin or a nonfunctional domain of MMIalpha. In GFP-actin cells, lysosomes displayed a combination of rapid long-range directional movements dependent on microtubules, short random movements, and pauses, sometimes on actin filaments. We showed that the inhibition of the dynamics of actin filaments by cytochalasin D increased pauses of lysosomes on actin structures, while depolymerization of actin filaments using latrunculin A increased the mobility of lysosomes but impaired the directionality of their long-range movements. The production of a nonfunctional domain of MMIalpha impaired the intracellular distribution of lysosomes and the directionality of their long-range movements. Altogether, our observations indicate for the first time that both actin filaments and MMIalpha contribute to the movement of lysosomes in cooperation with microtubules and their associated molecular motors.
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Affiliation(s)
- M N Cordonnier
- Morphogenèse et Signalisation Cellulaires, Unité Mixte de Recherche 144, Institut Curie, France
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65
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Abstract
Myosin VI is the only pointed end-directed myosin identified and is likely regulated by heavy chain phosphorylation (HCP) at the actin-binding site in vivo. We undertook a detailed kinetic analysis of the actomyosin VI ATPase cycle to determine whether there are unique adaptations to support reverse directionality and to determine the molecular basis of regulation by HCP. ADP release is the rate-limiting step in the cycle. ATP binds slowly and with low affinity. At physiological nucleotide concentrations, myosin VI is strongly bound to actin and populates the nucleotide-free (rigor) and ADP-bound states. Therefore, myosin VI is a high duty ratio motor adapted for maintaining tension and has potential to be processive. A mutant mimicking HCP increases the rate of P(i) release, which lowers the K(ATPase) but does not affect ADP release. These measurements are the first to directly measure the steps regulated by HCP for any myosin. Measurements with double-headed myosin VI demonstrate that the heads are not independent, and the native dimer hydrolyzes multiple ATPs per diffusional encounter with an actin filament. We propose an alternating site model for the stepping and processivity of two-headed high duty ratio myosins.
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Affiliation(s)
- E M De La Cruz
- Department of Physiology, Pennsylvania Muscle Institute, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, Philadelphia, Pennsylvania 19104-6085, USA
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66
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Abstract
Myosin-I is the single-headed, membrane binding member of the myosin superfamily that plays a role in membrane dynamics and transport [1-6]. Its molecular functions and its mechanism of regulation are not known. In mammalian cells, myosin-I is excluded from specific microfilament populations, indicating that its localization is tightly regulated. Identifying the mechanism of this localization, and the specific actin populations with which myosin-I interacts, is crucial to understanding the molecular functions of this motor. eGFP chimeras of myo1b [7] were imaged in live and fixed NRK cells. Ratio-imaging microscopy shows that myo1b-eGFP concentrates within dynamic areas of the actin cytoskeleton, most notably in membrane ruffles. Myo1b-eGFP does not associate with stable actin bundles or stress fibers. Truncation mutants consisting of the motor or tail domains show a partially overlapping cytoplasmic localization with full-length myo1b, but do not concentrate in membrane ruffles. A chimera consisting of the light chain and tail domains of myo1b and the motor domain from nonmuscle myosin-IIb (nmMIIb) concentrates on actin filaments in ruffles as well as to stress fibers. In vitro motility assays show that the exclusion of myo1b from certain actin filament populations is due to the regulation of the actomyosin interaction by tropomyosin. Therefore, we conclude that tropomyosin and spatially regulated actin polymerization play important roles in regulating the function and localization of myo1b.
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Affiliation(s)
- N Tang
- Department of Physiology and The Pennsylvania Muscle Institute, University of Pennsylvania School of Medicine, B400 Richards, Philadelphia, PA 19104, USA
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67
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Reck-Peterson SL, Tyska MJ, Novick PJ, Mooseker MS. The yeast class V myosins, Myo2p and Myo4p, are nonprocessive actin-based motors. J Cell Biol 2001; 153:1121-6. [PMID: 11381095 PMCID: PMC2174330 DOI: 10.1083/jcb.153.5.1121] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2001] [Accepted: 04/05/2001] [Indexed: 12/04/2022] Open
Abstract
The motor properties of the two yeast class V myosins, Myo2p and Myo4p, were examined using in vitro motility assays. Both myosins are active motors with maximum velocities of 4.5 microm/s for Myo2p and 1.1 microm/s for Myo4p. Myo2p motility is Ca(2+) insensitive. Both myosins have properties of a nonprocessive motor, unlike chick myosin-Va (M5a), which behaves as a processive motor when assayed under identical conditions. Additional support for the idea that Myo2p is a nonprocessive motor comes from actin cosedimentation assays, which show that Myo2p has a low affinity for F-actin in the presence of ATP and Ca(2+), unlike chick brain M5a. These studies suggest that if Myo2p functions in organelle transport, at least five molecules of Myo2p must be present per organelle to promote directed movement.
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Affiliation(s)
- Samara L. Reck-Peterson
- Department of Molecular, Cellular, and Developmental Biology
- Department of Cell Biology, Yale University, New Haven, Connecticut 06520
| | | | - Peter J. Novick
- Department of Cell Biology, Yale University, New Haven, Connecticut 06520
| | - Mark S. Mooseker
- Department of Molecular, Cellular, and Developmental Biology
- Department of Cell Biology, Yale University, New Haven, Connecticut 06520
- Department of Pathology, Yale University, New Haven, Connecticut 06520
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68
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Weiss S, Chizhov I, Geeves MA. A flash photolysis fluorescence/light scattering apparatus for use with sub microgram quantities of muscle proteins. J Muscle Res Cell Motil 2001; 21:423-32. [PMID: 11129433 DOI: 10.1023/a:1005690106951] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Transient kinetic methods such as stopped flow and quenched flow have been used to elucidate many of the fundamental features of the molecular interactions which underlie muscle contraction. However, these methods traditionally require relatively large amounts of protein (10(-3) g) and so have been used most effectively for the proteins purified from bulk muscle tissue of large animals or where the proteins can be expressed in large amounts (e.g.. Dictyostelium). We have investigated the use of flash photolysis of an inert precursor of ATP (cATP) to initiate the dissociation of acto.S1 and acto.myosin and the subsequent ATP turnover reaction. Using a sample volume of 10 microl we show that a significant amount of information on the transient and steady-state kinetics of the system can be obtained from a sample containing just 50 nM of acto.myosin or acto.S1 complex in solution. Therefore in presence of excess of one protein component the measurements require only 250 ng myosin, 62 ng S1 or 25 ng actin. This is therefore the method of choice for kinetic analysis of acto.myosins which are only available in microgram quantities. We report for the first time the determination of the second order rate constant of ATP-induced dissociation of actin from the myosin extracted from a single fibre from a rabbit psoas muscle.
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Affiliation(s)
- S Weiss
- Research School of Biosciences, University of Kent, Canterbury, Kent, UK
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69
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Sokac AM, Bement WM. Regulation and expression of metazoan unconventional myosins. INTERNATIONAL REVIEW OF CYTOLOGY 2001; 200:197-304. [PMID: 10965469 DOI: 10.1016/s0074-7696(00)00005-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Unconventional myosins are molecular motors that convert adenosine triphosphate (ATP) hydrolysis into movement along actin filaments. On the basis of primary structure analysis, these myosins are represented by at least 15 distinct classes (classes 1 and 3-16), each of which is presumed to play a specific cellular role. However, in contrast to the conventional myosins-2, which drive muscle contraction and cytokinesis and have been studied intensively for many years in both uni- and multicellular organisms, unconventional myosins have only been subject to analysis in metazoan systems for a short time. Here we critically review what is known about unconventional myosin regulation, function, and expression. Several points emerge from this analysis. First, in spite of the high relative conservation of motor domains among the myosin classes, significant differences are found in biochemical and enzymatic properties of these motor domains. Second, the idea that characteristic distributions of unconventional myosins are solely dependent on the myosin tail domain is almost certainly an oversimplification. Third, the notion that most unconventional myosins function as transport motors for membranous organelles is challenged by recent data. Finally, we present a scheme that clarifies relationships between various modes of myosin regulation.
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Affiliation(s)
- A M Sokac
- Program in Cellular and Molecular Biology, University of Wisconsin, Madison 53706, USA
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70
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Affiliation(s)
- N Osherov
- Division of Pathology and Laboratory Medicine, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA
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71
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Hudspeth AJ, Choe Y, Mehta AD, Martin P. Putting ion channels to work: mechanoelectrical transduction, adaptation, and amplification by hair cells. Proc Natl Acad Sci U S A 2000; 97:11765-72. [PMID: 11050207 PMCID: PMC34347 DOI: 10.1073/pnas.97.22.11765] [Citation(s) in RCA: 206] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
As in other excitable cells, the ion channels of sensory receptors produce electrical signals that constitute the cellular response to stimulation. In photoreceptors, olfactory neurons, and some gustatory receptors, these channels essentially report the results of antecedent events in a cascade of chemical reactions. The mechanoelectrical transduction channels of hair cells, by contrast, are coupled directly to the stimulus. As a consequence, the mechanical properties of these channels shape our hearing process from the outset of transduction. Channel gating introduces nonlinearities prominent enough to be measured and even heard. Channels provide a feedback signal that controls the transducer's adaptation to large stimuli. Finally, transduction channels participate in an amplificatory process that sensitizes and sharpens hearing.
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Affiliation(s)
- A J Hudspeth
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, 1230 York Avenue, New York, NY 10021-6399, USA.
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72
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Abstract
The kinetic mechanism of myosin V is of great interest because recent evidence indicates that the two-headed myosin V molecule functions as a processive motor, i.e., myosin V is capable of moving along an actin filament for many catalytic cycles of the motor without dissociating. Three recent publications assessing the kinetics of single-headed myosin V provide different conclusions regarding the mechanism, particularly the rate-limiting step of the cycle. One study (, Proc. Natl. Acad. Sci. USA. 96:13726-13731) identifies ADP release as the rate-limiting step and provides a kinetic explanation for myosin V processivity. The others (, J. Biol. Chem. 274:27448-27456;, J. Biol. Chem. 275:4329-4335) do not identify the rate-limiting step but conclude that it is not ADP release. We show experimental and simulated data demonstrating that the inconsistencies in the reports may be due to difficulties in the measurement of the steady-state ATPase rate. Under standard assay conditions, ADP competes with ATP, resulting in product inhibition of the ATPase rate. This presents technical problems in analyzing and interpreting the kinetics of myosin V and likely of other members of the myosin family with high ADP affinities.
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Affiliation(s)
- E M De La Cruz
- University of Pennsylvania School of Medicine, Department of Physiology, and the Pennsylvania Muscle Institute, Philadelphia, Pennsylvania 19104-6085 USA
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73
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Abstract
Members of the myosin superfamily of actin-based motor proteins were previously thought to move only towards the barbed end of the actin filament. In an extraordinary reversal of this dogma, an abundant and widespread unconventional myosin known as myosin VI has recently been shown to move towards the pointed end of the actin filament - the opposite direction of all other characterized myosins. This discovery raises novel and intriguing questions about the molecular mechanisms of reversal and the biological roles of this 'backwards' myosin.
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Affiliation(s)
- O C Rodriguez
- Dept of Cell and Molecular Physiology, School of Medicine, University of North Carolina at Chapel Hill, 27599-7545, USA
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74
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Geeves MA, Perreault-Micale C, Coluccio LM. Kinetic analyses of a truncated mammalian myosin I suggest a novel isomerization event preceding nucleotide binding. J Biol Chem 2000; 275:21624-30. [PMID: 10781577 DOI: 10.1074/jbc.m000342200] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MI(1IQ) is a complex of calmodulin and an epitope-tagged 85-kDa fragment representing the amino-terminal catalytic motor domain and the first of 6 calmodulin-binding IQ domains of the mammalian myosin I gene, rat myr-1 (130-kDa myosin I or MI(130)). We have determined the transient kinetic parameters that dictate the ATP hydrolysis cycle of mammalian myosin I by examining the properties of MI(1IQ). Transient kinetics reveal that the affinity of MI(1IQ) for actin is 12 nm. The ATP-induced dissociation of actin-MI(1IQ) is biphasic. The fast phase is dependent upon [ATP], whereas the slow phase is not; both phases show a Ca(2+) sensitivity. The fast phase is eliminated by the addition of ADP, 10 micrometer being required for half-saturation of the effect in the presence of Ca(2+) and 3 micrometer ADP in the absence of Ca(2+). The slow phase shares the same rate constant as ADP release (8 and 3 s(-)(1) in the presence and absence of Ca(2+), respectively), but cannot be eliminated by decreasing [ADP]. We interpret these results to suggest that actin-myosin I exists in two forms in equilibrium, one of which is unable to bind nucleotide. These results also indicate that the absence of the COOH-terminal 5 calmodulin binding domains of myr-1 do not influence the kinetic properties of MI(130) and that the Ca(2+) sensitivity of the kinetics are in all likelihood due to Ca(2+) binding to the first IQ domain.
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Affiliation(s)
- M A Geeves
- Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom and the Boston Biomedical Research Institute, Watertown, Massachusetts 02472, USA.
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75
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Perreault-Micale C, Shushan AD, Coluccio LM. Truncation of a mammalian myosin I results in loss of Ca2+-sensitive motility. J Biol Chem 2000; 275:21618-23. [PMID: 10777479 DOI: 10.1074/jbc.m000363200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MYR-1, a mammalian class I myosin, consisting of a heavy chain and 4-6 associated calmodulins, is represented by the 130-kDa myosin I (or MI(130)) from rat liver. MI(130) translocates actin filaments in vitro in a Ca(2+)-regulated manner. A decrease in motility observed at higher Ca(2+) concentrations has been attributed to calmodulin dissociation. To investigate mammalian myosin I regulation, we have coexpressed in baculovirus calmodulin and an epitope-tagged 85-kDa fragment representing the amino-terminal catalytic "motor" domain and the first calmodulin-binding IQ domain of rat myr-1; we refer to this truncated molecule here as MI(1IQ). Association of calmodulin to MI(1IQ) is Ca(2+)-insensitive. MI(1IQ) translocates actin filaments in vitro at a rate resembling MI(130), but unlike MI(130), does not exhibit sensitivity to 0.1-100 micrometer Ca(2+). In addition to demonstrating successful expression of a functional truncated mammalian myosin I in vitro, these results indicate that: 1) Ca(2+)-induced calmodulin dissociation from MI(130) in the presence of actin is not from the first IQ domain, 2) velocity is not affected by the length of the IQ region, and 3) the Ca(2+) sensitivity of actin translocation exhibited by MI(130) involves 1 or more of the other 5 IQ domains and/or the carboxyl tail.
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Affiliation(s)
- C Perreault-Micale
- Boston Biomedical Research Institute, Watertown, Massachusetts 02472, USA
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76
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Barylko B, Binns DD, Albanesi JP. Regulation of the enzymatic and motor activities of myosin I. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1496:23-35. [PMID: 10722874 DOI: 10.1016/s0167-4889(00)00006-9] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Myosins I were the first unconventional myosins to be purified and they remain the best characterized. They have been implicated in various motile processes, including organelle translocation, ion channel gating and cytoskeletal reorganization but their exact cellular functions are still unclear. All members of the myosin I family, from yeast to man, have three structural domains: a catalytic head domain that binds ATP and actin; a tail domain believed to be involved in targeting the myosins to specific subcellular locations and a junction or neck domain that connects them and interacts with light chains. In this review we discuss how each of these three domains contributes to the regulation of myosin I enzymatic activity, motor activity and subcellular localization.
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Affiliation(s)
- B Barylko
- Department of Pharmacology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75235-9041, USA.
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77
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Wang F, Chen L, Arcucci O, Harvey EV, Bowers B, Xu Y, Hammer JA, Sellers JR. Effect of ADP and ionic strength on the kinetic and motile properties of recombinant mouse myosin V. J Biol Chem 2000; 275:4329-35. [PMID: 10660602 DOI: 10.1074/jbc.275.6.4329] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mouse myosin V is a two-headed unconventional myosin with an extended neck that binds six calmodulins. Double-headed (heavy meromyosin-like) and single-headed (subfragment 1-like) fragments of mouse myosin V were expressed in Sf9 cells, and intact myosin V was purified from mouse brain. The actin-activated MgATPase of the tissue-purified myosin V, and its expressed fragments had a high V(max) and a low K(ATPase). Calcium regulated the MgATPase of intact myosin V but not of the fragments. Both the MgATPase activity and the in vitro motility were remarkably insensitive to ionic strength. Myosin V and its fragments translocated actin at very low myosin surface densities. ADP markedly inhibited the actin-activated MgATPase activity and the in vitro motility. ADP dissociated from myosin V subfragment 1 at a rate of about 11.5 s(-1) under conditions where the V(max) was 3.3 s(-1), indicating that, although not totally rate-limiting, ADP dissociation was close to the rate-limiting step. The high affinity for actin and the slow rate of ADP release helps the myosin head to remain attached to actin for a large fraction of each ATPase cycle and allows actin filaments to be moved by only a few myosin V molecules in vitro.
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Affiliation(s)
- F Wang
- Laboratory of Molecular Cardiology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA
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78
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Abstract
To date, fourteen classes of unconventional myosins have been identified. Recent reports have implicated a number of these myosins in organelle transport, and in the formation, maintenance and/or dynamics of actin-rich structures involved in a variety of cellular processes including endocytosis, cell migration, and sensory transduction. Characterizations of organelle dynamics in pigment cells and neurons have further defined the contributions made by unconventional myosins and microtubule motors to the transport and distribution of organelles. Several studies have provided evidence of complexes through which cooperative organelle transport may be coordinated. Finally, the myosin superfamily has been shown to contain at least one processive motor and one backwards motor.
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Affiliation(s)
- X Wu
- Laboratory of Cell Biology, Section on Molecular Cell Biology, National Institutes of Health, Bethesda, 20892-0301, USA
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