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Brizendine RK, Anuganti M, Cremo CR. Evidence for S2 flexibility by direct visualization of quantum dot-labeled myosin heads and rods within smooth muscle myosin filaments moving on actin in vitro. J Gen Physiol 2021; 153:211680. [PMID: 33439241 PMCID: PMC7809879 DOI: 10.1085/jgp.202012751] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 11/18/2020] [Accepted: 12/10/2020] [Indexed: 12/21/2022] Open
Abstract
Myosins in muscle assemble into filaments by interactions between the C-terminal light meromyosin (LMM) subdomains of the coiled-coil rod domain. The two head domains are connected to LMM by the subfragment-2 (S2) subdomain of the rod. Our mixed kinetic model predicts that the flexibility and length of S2 that can be pulled away from the filament affects the maximum distance working heads can move a filament unimpeded by actin-attached heads. It also suggests that it should be possible to observe a head remain stationary relative to the filament backbone while bound to actin (dwell), followed immediately by a measurable jump upon detachment to regain the backbone trajectory. We tested these predictions by observing filaments moving along actin at varying ATP using TIRF microscopy. We simultaneously tracked two different color quantum dots (QDs), one attached to a regulatory light chain on the lever arm and the other attached to an LMM in the filament backbone. We identified events (dwells followed by jumps) by comparing the trajectories of the QDs. The average dwell times were consistent with known kinetics of the actomyosin system, and the distribution of the waiting time between observed events was consistent with a Poisson process and the expected ATPase rate. Geometric constraints suggest a maximum of ∼26 nm of S2 can be unzipped from the filament, presumably involving disruption in the coiled-coil S2, a result consistent with observations by others of S2 protruding from the filament in muscle. We propose that sufficient force is available from the working heads in the filament to overcome the stiffness imposed by filament-S2 interactions.
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Affiliation(s)
- Richard K Brizendine
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Reno, NV
| | - Murali Anuganti
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Reno, NV
| | - Christine R Cremo
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Reno, NV
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2
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Klinov DV, Protopopova AD, Andrianov DS, Litvinov RI, Weisel JW. An Improved Substrate for Superior Imaging of Individual Biomacromolecules with Atomic Force Microscopy. Colloids Surf B Biointerfaces 2020; 196:111321. [DOI: 10.1016/j.colsurfb.2020.111321] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 08/07/2020] [Accepted: 08/11/2020] [Indexed: 12/12/2022]
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3
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Obeid S, Guyomarc'h F. Atomic force microscopy of food assembly: Structural and mechanical insights at the nanoscale and potential opportunities from other fields. FOOD BIOSCI 2020. [DOI: 10.1016/j.fbio.2020.100654] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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4
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Kodera N, Ando T. High-Speed Atomic Force Microscopy to Study Myosin Motility. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1239:127-152. [PMID: 32451858 DOI: 10.1007/978-3-030-38062-5_7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
High-speed atomic force microscopy (HS-AFM) is a unique tool that enables imaging of protein molecules during their functional activity at sub-100 ms temporal and submolecular spatial resolution. HS-AFM is suited for the study of highly dynamic proteins, including myosin motors. HS-AFM images of myosin V walking on actin filaments provide irrefutable evidence for the swinging lever arm motion propelling the molecule forward. Moreover, molecular behaviors that have not been noticed before are also displayed on the AFM movies. This chapter describes the principle, underlying techniques and performance of HS-AFM, filmed images of myosin V, and mechanistic insights into myosin motility provided from the filmed images.
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Affiliation(s)
- Noriyuki Kodera
- Nano Life Science Institute (WPI NanoLSI), Kanazawa University, Kanazawa, Japan
| | - Toshio Ando
- Nano Life Science Institute (WPI NanoLSI), Kanazawa University, Kanazawa, Japan.
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5
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Varizhuk AM, Protopopova AD, Tsvetkov VB, Barinov NA, Podgorsky VV, Tankevich MV, Vlasenok MA, Severov VV, Smirnov IP, Dubrovin EV, Klinov DV, Pozmogova GE. Polymorphism of G4 associates: from stacks to wires via interlocks. Nucleic Acids Res 2018; 46:8978-8992. [PMID: 30107602 PMCID: PMC6158749 DOI: 10.1093/nar/gky729] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2018] [Revised: 07/30/2018] [Accepted: 07/31/2018] [Indexed: 01/16/2023] Open
Abstract
We examined the assembly of DNA G-quadruplexes (G4s) into higher-order structures using atomic force microscopy, optical and electrophoretic methods, NMR spectroscopy and molecular modeling. Our results suggest that parallel blunt-ended G4s with single-nucleotide or modified loops may form different types of multimers, ranging from stacks of intramolecular structures and/or interlocked dimers and trimers to wires. Decreasing the annealing rate and increasing salt or oligonucleotide concentrations shifted the equilibrium from intramolecular G4s to higher-order structures. Control antiparallel and hybrid G4s demonstrated no polymorphism or aggregation in our experiments. The modification that mimics abasic sites (1',2'-dideoxyribose residues) in loops enhanced the oligomerization/multimerization of both the 2-tetrad and 3-tetrad G4 motifs. Our results shed light on the rules that govern G4 rearrangements. Gaining control over G4 folding enables the harnessing of the full potential of such structures for guided assembly of supramolecular DNA structures for nanotechnology.
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Affiliation(s)
- Anna M Varizhuk
- Biophysics Department, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow 119435, Russia
| | - Anna D Protopopova
- Biophysics Department, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow 119435, Russia
| | - Vladimir B Tsvetkov
- Biophysics Department, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow 119435, Russia
| | - Nikolay A Barinov
- Biophysics Department, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow 119435, Russia
| | - Victor V Podgorsky
- Biophysics Department, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow 119435, Russia
| | - Maria V Tankevich
- Biophysics Department, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow 119435, Russia
| | - Maria A Vlasenok
- Biophysics Department, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow 119435, Russia
| | - Vyacheslav V Severov
- Biophysics Department, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow 119435, Russia
| | - Igor P Smirnov
- Biophysics Department, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow 119435, Russia
| | - Evgeniy V Dubrovin
- Biophysics Department, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow 119435, Russia
| | - Dmitry V Klinov
- Biophysics Department, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow 119435, Russia
| | - Galina E Pozmogova
- Biophysics Department, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow 119435, Russia
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6
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Protopopova AD, Litvinov RI, Galanakis DK, Nagaswami C, Barinov NA, Mukhitov AR, Klinov DV, Weisel JW. Morphometric characterization of fibrinogen's αC regions and their role in fibrin self-assembly and molecular organization. NANOSCALE 2017; 9:13707-13716. [PMID: 28884176 PMCID: PMC6501582 DOI: 10.1039/c7nr04413e] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The flexible C-terminal parts of fibrinogen's Aα chains named the αC regions have been shown to play a role in fibrin self-assembly, although many aspects of their structure and functions remain unknown. To examine the involvement of the αC regions in the early stages of fibrin formation, we used high-resolution atomic force microscopy to image fibrinogen and oligomeric fibrin. Plasma-purified full-length human fibrinogen or des-αC fibrinogen lacking most of the αC regions, untreated or treated with thrombin, was imaged. Up to 80% of the potentially existing αC regions were visualized and quantified; they were highly heterogeneous in their length and configurations. Conversion of fibrinogen to fibrin was accompanied by an increase in the incidence and length of the αC regions as well as transitions from more compact conformations, such as a globule on a string, to extended and more flexible offshoots. Concurrent dynamic turbidimetry, confocal microscopy, and scanning electron microscopy revealed that trimming of the αC regions slowed down fibrin formation, which correlated with longer protofibrils, thinner fibers, and a denser network. No structural distinctions, except for the incidence of the αC regions, were revealed in the laterally aggregated protofibrils made of the full-length or des-αC fibrinogens, suggesting a pure kinetic effect of the αC regions on the fibrin architecture. This work provides a structural molecular basis for the promoting role of the αC regions in the early stages of fibrin self-assembly and reveals this stage of fibrin formation as a potential therapeutic target to modulate the structure and mechanical properties of blood clots.
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Affiliation(s)
- Anna D Protopopova
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.
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7
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Matusovsky OS, Shevchenko UV, Matusovskaya GG, Sobieszek A, Dobrzhanskaya AV, Shelud’ko NS. Catch muscle myorod modulates ATPase activity of Myosin in a phosphorylation-dependent way. PLoS One 2015; 10:e0125379. [PMID: 25915932 PMCID: PMC4410989 DOI: 10.1371/journal.pone.0125379] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 03/23/2015] [Indexed: 11/18/2022] Open
Abstract
Myorod is expressed exclusively in molluscan catch muscle and localizes on the surface of thick filaments together with twitchin and myosin. Myorod is an alternatively spliced product of the myosin heavy-chain gene that contains the C-terminal rod part of myosin and a unique N-terminal domain. The unique domain is a target for phosphorylation by gizzard smooth myosin light chain kinase (smMLCK) and, perhaps, molluscan twitchin, which contains a MLCK-like domain. To elucidate the role of myorod and its phosphorylation in the catch muscle, the effect of chromatographically purified myorod on the actin-activated Mg2+-ATPase activity of myosin was studied. We found that phosphorylation at the N-terminus of myorod potentiated the actin-activated Mg2+-ATPase activity of mussel and rabbit myosins. This potentiation occurred only if myorod was phosphorylated and introduced into the ATPase assay as a co-filament with myosin. We suggest that myorod could be related to the catch state, a function specific to molluscan muscle.
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Affiliation(s)
- Oleg S. Matusovsky
- A.V. Zhirmunsky Institute of Marine Biology, Far East Branch of the Russian Academy of Sciences, Vladivostok, Russia
- School of Biomedicine, Far Eastern Federal University, Vladivostok, Russia
- * E-mail: (OM); (NS)
| | - Ulyana V. Shevchenko
- A.V. Zhirmunsky Institute of Marine Biology, Far East Branch of the Russian Academy of Sciences, Vladivostok, Russia
| | - Galina G. Matusovskaya
- A.V. Zhirmunsky Institute of Marine Biology, Far East Branch of the Russian Academy of Sciences, Vladivostok, Russia
| | - Apolinary Sobieszek
- Institute for Biomedical Aging Research, Austrian Academy of Sciences, Innsbruck, Austria
| | - Anna V. Dobrzhanskaya
- A.V. Zhirmunsky Institute of Marine Biology, Far East Branch of the Russian Academy of Sciences, Vladivostok, Russia
| | - Nikolay S. Shelud’ko
- A.V. Zhirmunsky Institute of Marine Biology, Far East Branch of the Russian Academy of Sciences, Vladivostok, Russia
- * E-mail: (OM); (NS)
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Broad disorder and the allosteric mechanism of myosin II regulation by phosphorylation. Proc Natl Acad Sci U S A 2011; 108:8218-23. [PMID: 21536903 DOI: 10.1073/pnas.1014137108] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Double electron electron resonance EPR methods was used to measure the effects of the allosteric modulators, phosphorylation, and ATP, on the distances and distance distributions between the two regulatory light chain of myosin (RLC). Three different states of smooth muscle myosin (SMM) were studied: monomers, the short-tailed subfragment heavy meromyosin, and SMM filaments. We reconstituted myosin with nine single cysteine spin-labeled RLC. For all mutants we found a broad distribution of distances that could not be explained by spin-label rotamer diversity. For SMM and heavy meromyosin, several sites showed two heterogeneous populations in the unphosphorylated samples, whereas only one was observed after phosphorylation. The data were consistent with the presence of two coexisting heterogeneous populations of structures in the unphosphorylated samples. The two populations were attributed to an on and off state by comparing data from unphosphorylated and phosphorylated samples. Models of these two states were generated using a rigid body docking approach derived from EM [Wendt T, Taylor D, Trybus KM, Taylor K (2001) Proc Natl Acad Sci USA 98:4361-4366] (PNAS, 2001, 98:4361-4366), but our data revealed a new feature of the off-state, which is heterogeneity in the orientation of the two RLC. Our average off-state structure was very similar to the Wendt model reveal a new feature of the off state, which is heterogeneity in the orientations of the two RLC. As found previously in the EM study, our on-state structure was completely different from the off-state structure. The heads are splayed out and there is even more heterogeneity in the orientations of the two RLC.
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9
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Czajkowsky DM, Shao Z. The human IgM pentamer is a mushroom-shaped molecule with a flexural bias. Proc Natl Acad Sci U S A 2009; 106:14960-5. [PMID: 19706439 PMCID: PMC2736442 DOI: 10.1073/pnas.0903805106] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Indexed: 01/08/2023] Open
Abstract
The textbook planar model of pentameric IgM, a potent activator of complement C1q, is based upon the crystallographic structure of IgG. Although widely accepted, key predictions of this model have not yet been directly confirmed, which is particularly important since IgG lacks a major Ig fold domain in its Fc region that is present in IgM. Here, we construct a homology-based structural model of the IgM pentamer using the recently obtained crystallographic structure of IgE Fc, which has this additional Ig domain, under the constraint that all of the cysteine residues known to form disulfide bridges both within each monomer and between monomers are bonded together. In contrast to the planar model, this model predicts a non-planar, mushroom-shaped complex, with the central portion formed by the C-terminal domains protruding out of the plane formed by the Fab domains. This unexpected conformation of IgM is, however, directly confirmed by cryo-atomic force microscopy of individual human IgM molecules. Further analysis of this model with free energy calculations of out-of-plane Fab domain rotations reveals a pronounced asymmetry favoring flexions toward the central protrusion. This bias, together with polyvalent attachment to cell surface antigen, would ensure that the IgM pentamer is oriented on the cell membrane with its C1q binding sites fully exposed to the solution, and thus provides a mechanistic explanation for the first steps of C1q activation by IgM.
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Affiliation(s)
- Daniel M. Czajkowsky
- Department of Molecular Physiology and Biological Physics, University of Virginia Health Sciences Center, P.O. Box 800736, Charlottesville, VA 22908; and
| | - Zhifeng Shao
- Department of Molecular Physiology and Biological Physics, University of Virginia Health Sciences Center, P.O. Box 800736, Charlottesville, VA 22908; and
- Systems Biomedicine, Shanghai Jiao Tong University, Shanghai 200240, China
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10
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Jensenius H, Klein DCG, van Hecke M, Oosterkamp TH, Schmidt T, Jensenius JC. Mannan-binding lectin: structure, oligomerization, and flexibility studied by atomic force microscopy. J Mol Biol 2009; 391:246-59. [PMID: 19501100 DOI: 10.1016/j.jmb.2009.05.083] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2009] [Revised: 05/27/2009] [Accepted: 05/29/2009] [Indexed: 10/20/2022]
Abstract
Mannan-binding lectin (MBL) is the archetypical pathogen recognition molecule of the innate immune defense. Upon binding to microorganisms, reactions leading to the destruction of the offender ensue. MBL is an oligomer of structural subunits each composed of three identical polypeptides. We used atomic force microscopy to reveal tertiary and quaternary structures of MBL. The images in both air and buffer show a quaternary structure best described as "sertiform", that is, a hub from which the subunits fan out. The dimensions conform to those calculated from primary and secondary structures. The subunits associate with a preferred angle of 40 degrees between them. This angle is stable with respect to the degree of oligomerization for MBL of four subunits or more. Due to an interruption in the collagenous sequence, the arms of the subunits are expected to form a kink. We find that approximately 30% of the subunits are kinked and the kink angle distributed, quite broadly, around 145 degrees . The conformation and flexibility of the MBL molecule that we observe differ distinctly from the popular view of a "bouquet-like" configuration as that found for related members of the complement system such as C1q. This structural information will further the understanding of the specific functioning of the MBL pathway of complement activation.
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Affiliation(s)
- Henriette Jensenius
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, Leiden, The Netherlands
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11
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Ikebe M. Regulation of the function of mammalian myosin and its conformational change. Biochem Biophys Res Commun 2008; 369:157-64. [PMID: 18211803 DOI: 10.1016/j.bbrc.2008.01.057] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2007] [Accepted: 01/03/2008] [Indexed: 12/01/2022]
Abstract
It has been known that the phosphorylation of the regulatory light chain, residing at the head/rod junction of the molecule activates the motor activity of smooth muscle and non-muscle conventional myosin (myosin II), and triggers a large conformational change of the molecule from the inhibited folded conformation to the active extended conformation. Recent structural analysis has revealed the structural basis of the inhibition of the motor function of the two heads in the inhibited conformation. On the other hand, recent studies have revealed that a processive unconventional myosin, myosin V, also shows a large change in the conformation from the folded to an extended form and this explains the activation mechanism of myosin V motor activity. These findings suggest the presence of a common scenario for the regulation of motor protein functions.
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Affiliation(s)
- Mitsuo Ikebe
- Department of Physiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA
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12
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An historical perspective on cell mechanics. Pflugers Arch 2007; 456:3-12. [DOI: 10.1007/s00424-007-0405-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Revised: 11/12/2007] [Accepted: 11/15/2007] [Indexed: 11/26/2022]
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13
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Ip K, Sobieszek A, Solomon D, Jiao Y, Paré PD, Seow CY. Physical integrity of smooth muscle myosin filaments is enhanced by phosphorylation of the regulatory myosin light chain. Cell Physiol Biochem 2007; 20:649-58. [PMID: 17762191 DOI: 10.1159/000107548] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/04/2007] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND AND AIMS Smooth muscle myosin monomers self-assemble in solution to form filaments. Phosphorylation of the 20-kD regulatory myosin light chain (MLC20) enhances filament formation. It is not known whether the phosphorylated and non-phosphorylated filaments possess the same structural integrity. METHODS We purified myosin from bovine trachealis to form filaments, in ATP-containing zero-calcium solution during a slow dialysis that gradually reduced the ionic strength. Sufficient myosin light chain kinase and phosphatase, as well as calmodulin, were retained after the myosin purification and this enabled phosphorylation of MLC20 within 20-40s after addition of calcium to the filament suspension. The phosphorylated and non-phosphorylated filaments were then partially disassembled by ultrasonification. The extent of filament disintegration was visualized and quantified by atomic force microscopy. RESULTS MLC20 phosphorylation reduced the diameter of the filaments and rendered the filaments more resistant to ultrasonic agitation. Electron microscopy revealed a similar reduction in filament diameter in intact smooth muscle when the cells were activated. CONCLUSION Modification of the structural and physical properties of myosin filaments by MLC20 phosphorylation may be a key regulation step in smooth muscle where formation and dissolution of the filaments are required in the cells' adaptation to different cell length.
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Affiliation(s)
- Kelvin Ip
- James Hogg iCAPTURE Centre, St. Paul's Hospital, Vancouver, Canada
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14
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Burgess SA, Yu S, Walker ML, Hawkins RJ, Chalovich JM, Knight PJ. Structures of smooth muscle myosin and heavy meromyosin in the folded, shutdown state. J Mol Biol 2007; 372:1165-78. [PMID: 17707861 DOI: 10.1016/j.jmb.2007.07.014] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2007] [Revised: 06/29/2007] [Accepted: 07/09/2007] [Indexed: 11/23/2022]
Abstract
Remodelling the contractile apparatus within smooth muscle cells allows effective contractile activity over a wide range of cell lengths. Thick filaments may be redistributed via depolymerisation into inactive myosin monomers that have been detected in vitro, in which the long tail has a folded conformation. Using negative stain electron microscopy of individual folded myosin molecules from turkey gizzard smooth muscle, we show that they are more compact than previously described, with heads and the three segments of the folded tail closely packed. Heavy meromyosin (HMM), which lacks two-thirds of the tail, closely resembles the equivalent parts of whole myosin. Image processing reveals a characteristic head region morphology for both HMM and myosin, with features identifiable by comparison with less compact molecules. The two heads associate asymmetrically: the tip of one motor domain touches the base of the other, resembling the blocked and free heads of this HMM when it forms 2D crystals on lipid monolayers. The tail of HMM lies between the heads, contacting the blocked motor domain, unlike in the 2D crystal. The tail of whole myosin is bent sharply and consistently close to residues 1175 and 1535. The first bend position correlates with a skip in the coiled coil sequence, the second does not. Tail segments 2 and 3 associate only with the blocked head, such that the second bend is near the C-lobe of the blocked head regulatory light chain. Quantitative analysis of tail flexibility shows that the single coiled coil of HMM has an apparent Young's modulus of about 0.5 GPa. The folded tail of the whole myosin is less flexible, indicating interactions between the segments. The folded tail does not modify the compact head arrangement but stabilises it, indicating a structural mechanism for the very low ATPase activity of the folded molecule.
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Affiliation(s)
- Stan A Burgess
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK
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15
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Salzameda B, Facemyer KC, Beck BW, Cremo CR. The N-terminal lobes of both regulatory light chains interact with the tail domain in the 10 S-inhibited conformation of smooth muscle myosin. J Biol Chem 2006; 281:38801-11. [PMID: 17012238 DOI: 10.1074/jbc.m606555200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the presence of ATP, unphosphorylated smooth muscle myosin can form a catalytically inactive monomer that sediments at 10 Svedbergs (10 S). The tail of 10 S bends into thirds and interacts with the regulatory domain. ADP-P(i) is "trapped" at the active site, and consequently the ATPase activity is extremely low. We are interested in the structural basis for maintenance of this off state. Our prior photocross-linking work with 10 S showed that tail residues 1554-1583 are proximal to position 108 in the C-terminal lobe of one of the two regulatory light chains ( Olney, J. J., Sellers, J. R., and Cremo, C. R. (1996) J. Biol. Chem. 271, 20375-20384 ). These data suggested that the tail interacts with only one of the two regulatory light chains. Here we present data, using a photocross-linker on position 59 on the N-terminal lobe of the regulatory light chain (RLC), demonstrating that both regulatory light chains of a single molecule can cross-link to the light meromyosin portion of the tail. Mass spectrometric data show four specific cross-linked regions spanning residues 1428-1571 in the light meromyosin portion of the tail, consistent with cross-linking two RLC to one light meromyosin. In addition, we find that position 59 can cross-link internally to residues 42-45 within the same RLC subunit. The internal cross-link only forms in 10 S and not in unphosphorylated heavy meromyosin (lacking the light meromyosin), suggesting a structural rearrangement within the RLC attributed to the interaction of the tail with the head.
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Affiliation(s)
- Bridget Salzameda
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Nevada, 1664 N. Virginia Street, Reno, NV 89557, USA
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16
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Sheng S, Czajkowsky DM, Shao Z. Localization of linker histone in chromatosomes by cryo-atomic force microscopy. Biophys J 2006; 91:L35-7. [PMID: 16782797 PMCID: PMC1518653 DOI: 10.1529/biophysj.106.090423] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Linker histones play a fundamental role in determining higher order chromatin structure as a consequence of their association with nucelosomal DNA. Yet the locations and structural consequences of linker histone binding are still enigmatic. Here, using cryo-atomic force microscopy, we show that the linker histone H5 in native chromatin and in chromatosomes reconstituted on the 5S rDNA template is located at the dyad of the nucleosome core particle, within the "stem" structure. Direct measurement also indicates that the length of free linker DNA between chromatosomes in native chromatin is approximately 30 bp, slightly shorter than that estimated from nuclease digestion assays.
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Affiliation(s)
- Sitong Sheng
- Department of Molecular Physiology and Biological Physics, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA
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17
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Rovner AS, Fagnant PM, Trybus KM. Phosphorylation of a single head of smooth muscle myosin activates the whole molecule. Biochemistry 2006; 45:5280-9. [PMID: 16618116 PMCID: PMC2505275 DOI: 10.1021/bi060154c] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Regulatory light chain (RLC) phosphorylation activates smooth and non-muscle myosin II, but it has not been established if phosphorylation of one head turns on the whole molecule. Baculovirus expression and affinity chromatography were used to isolate heavy meromyosin (HMM) containing one phosphorylated and one dephosphorylated RLC (1-P HMM). Motility and steady-state ATPase assays indicated that 1-P HMM is nearly as active as HMM with two phosphorylated heads (2-P HMM). Single-turnover experiments further showed that both the dephosphorylated and phosphorylated heads of 1-P HMM can be activated by actin. Singly phosphorylated full-length myosin was also an active species with two cycling heads. Our results suggest that phosphorylation of one RLC abolishes the asymmetric inhibited state formed by dephosphorylated myosin [Liu, J., et al. (2003) J. Mol. Biol. 329, 963-972], allowing activation of both the phosphorylated and dephosphorylated heads. These findings help explain how smooth muscles are able to generate high levels of stress with low phosphorylation levels.
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Affiliation(s)
- Arthur S Rovner
- Department of Molecular Physiology and Biophysics, Health Sciences Research Facility, University of Vermont, Burlington, Vermont 05405-0068, USA
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Li HC, Song L, Salzameda B, Cremo CR, Fajer PG. Regulatory and catalytic domain dynamics of smooth muscle myosin filaments. Biochemistry 2006; 45:6212-21. [PMID: 16681394 PMCID: PMC5090715 DOI: 10.1021/bi060037h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Domain dynamics of the chicken gizzard smooth muscle myosin catalytic domain (heavy chain Cys-717) and regulatory domain (regulatory light chain Cys-108) were determined in the absence of nucleotides using saturation-transfer electron paramagnetic resonance. In unphosphorylated synthetic filaments, the effective rotational correlation times, tau(r), were 24 +/- 6 micros and 441 +/- 79 micros for the catalytic and regulatory domains, respectively. The corresponding amplitudes of motion were 42 +/- 4 degrees and 24 +/- 9 degrees as determined from steady-state phosphorescence anisotropy. These results suggest that the two domains have independent mobility due to a hinge between the two domains. Although a similar hinge was observed for skeletal myosin (Adhikari and Fajer (1997) Proc. Natl. Acad. Sci. U.S.A. 94, 9643-9647. Brown et al. (2001) Biochemistry 40, 8283-8291), the latter displayed higher regulatory domain mobility, tau(r)= 40 +/- 3 micros, suggesting a smooth muscle specific mechanism of constraining regulatory domain dynamics. In the myosin monomers the correlation times for both domains were the same (approximately 4 micros) for both smooth and skeletal myosin, suggesting that the motional difference between the two isoforms in the filaments was not due to intrinsic variation of hinge stiffness. Heavy chain/regulatory light chain chimeras of smooth and skeletal myosin pinpointed the origin of the restriction to the heavy chain and established correlation between the regulatory domain dynamics with the ability of myosin to switch off but not to switch on the ATPase and the actin sliding velocity. Phosphorylation of smooth muscle myosin filaments caused a small increase in the amplitude of motion of the regulatory domain (from 24 +/- 4 degrees to 36 +/- 7 degrees ) but did not significantly affect the rotational correlation time of the regulatory domain (441 to 408 micros) or the catalytic domain (24 to 17 micros). These data are not consistent with a stable interaction between the two catalytic domains in unphosphorylated smooth muscle myosin filaments in the absence of nucleotides.
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Affiliation(s)
| | | | | | | | - Piotr G. Fajer
- Author to whom correspondence should be addressed. Mailing address: Inst. Molecular Biophysics, Florida State University, Tallahassee, FL 32306. Tel: 850-645-1335. Fax: 850-644-1366.
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Somlyo AV, Khromov AS, Webb MR, Ferenczi MA, Trentham DR, He ZH, Sheng S, Shao Z, Somlyo AP. Smooth muscle myosin: regulation and properties. Philos Trans R Soc Lond B Biol Sci 2005; 359:1921-30. [PMID: 15647168 PMCID: PMC1693473 DOI: 10.1098/rstb.2004.1562] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The relationship of the biochemical states to the mechanical events in contraction of smooth muscle cross-bridges is reviewed. These studies use direct measurements of the kinetics of Pi and ADP release. The rate of release of Pi from thiophosphorylated cycling cross-bridges held isometric was biphasic with turnovers of 1.8 s-1 and 0.3 s-1, reflecting properties and forces directly acting on cross-bridges through mechanisms such as positive strain and inhibition by high-affinity MgADP binding. Fluorescent transients reporting release of an ADP analogue 3'-deac-edaADP were significantly faster in phasic than in tonic smooth muscles. Thiophosphorylation of myosin regulatory light chains (RLCs) increased and positive strain decreased the release rate around twofold. The rates of ADP release from rigor cross-bridges and the steady-state Pi release from cycling isometric cross-bridges are similar, indicating that the ADP-release step or an isomerization preceding it may limit the ATPase rate. Thus ADP release in phasic and tonic smooth muscles is a regulated step with strain- and dephosphorylation-dependence. High affinity of cross-bridges for ADP and slow ADP release prolong the fraction of the duty cycle occupied by strongly bound AM.ADP state(s) and contribute to the high economy of force that is characteristic of smooth muscle. RLC thiophosphorylation led to structural changes in smooth muscle cross-bridges consistent with our findings that thiophosphorylation and strain modulate product release.
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Affiliation(s)
- Avril V Somlyo
- Molecular Physiology and Biological Physics, University of Virginia, PO Box 800736, 1300 Jefferson Park Avenue, Charlottesville, VA 22908-0736, USA.
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Khromov AS, Webb MR, Ferenczi MA, Trentham DR, Somlyo AP, Somlyo AV. Myosin regulatory light chain phosphorylation and strain modulate adenosine diphosphate release from smooth muscle Myosin. Biophys J 2004; 86:2318-28. [PMID: 15041670 PMCID: PMC1304081 DOI: 10.1016/s0006-3495(04)74289-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The effects of myosin regulatory light chain (RLC) phosphorylation and strain on adenosine diphosphate (ADP) release from cross-bridges in phasic (rabbit bladder (Rbl)) and tonic (femoral artery (Rfa)) smooth muscle were determined by monitoring fluorescence transients of the novel ADP analog, 3'-deac-eda-ADP (deac-edaADP). Fluorescence transients reporting release of 3'-deac-eda-ADP were significantly faster in phasic (0.57 +/- 0.06 s(-1)) than tonic (0.29 +/- 0.03 s(-1)) smooth muscles. Thiophosphorylation of regulatory light chains increased and strain decreased the release rate approximately twofold. The calculated (k-ADP/k+ADP) dissociation constant, Kd of unstrained, unphosphorylated cross-bridges for ADP was 0.6 microM for rabbit bladder and 0.3 microM for femoral artery. The rates of ADP release from rigor bridges and reported values of Pi release (corresponding to the steady-state adenosine triphosphatase (ATPase) rate of actomyosin (AM)) from cross-bridges during a maintained isometric contraction are similar, indicating that the ADP-release step or an isomerization preceding it may be limiting the adenosine triphosphatase rate. We conclude that the strain- and dephosphorylation-dependent high affinity for and slow ADP release from smooth muscle myosin prolongs the fraction of the duty cycle occupied by strongly bound actomyosin.ADP state(s) and contributes to the high economy of force.
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Affiliation(s)
- Alexander S Khromov
- Molecular Physiology and Biological Physics, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA
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