Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.4.1 (myosin ATPase)
 1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Muscle-type creatine kinase (MM-CK) is a member of the CK isoenzyme family with key functions in cellular energetics. MM-CK interacts in an isoform-specific manner with the M-band of sarcomeric muscle, where it serves as an efficient intramyofibrillar ATP-regenerating system for the actin-activated myosin ATPase located nearby on both sides of the M-band. Four MM-CK-specific and highly conserved lysine residues are thought to be responsible for the interaction of MM-CK with the M-band. A yeast two-hybrid screen led to the identification of MM-CK as a binding partner of a central portion of myomesin (My7-8). An interaction was observed with domains six to eight of the closely related M-protein but not with several other Ig-like domains, including an M-band domain, of titin. The observed interactions were corroborated and characterised in detail by surface plasmon resonance spectroscopy (BiaCore). In both cases, they were CK isoform-specific and the MM-CK-specific lysine residues (K8. K24, K104 and K115) are involved in this interaction. At pH 6.8, the dissociation constants for the myomesin/MM-CK and the M-protein/MM-CK binding were in the range of 50-100 nM and around 1 microM, respectively. The binding showed pronounced pH-dependence and indicates a dynamic association/dissociation behaviour, which most likely depends on the energy state of the muscle. Our data propose a simple model for the regulation of this dynamic interaction.
J Mol Biol 2003 Sep 26
PMID:Muscle-type creatine kinase interacts with central domains of the M-band proteins myomesin and M-protein. 1297 58

Previous studies have shown that the renin-angiotensin system (RAS) is activated in diabetes and this may contribute to the subcellular remodelling and heart dysfunction in this disease. Therefore, we examined the effects of RAS blockade by enalapril, an angiotensin-converting enzyme inhibitor, and losartan, an angiotensin receptor AT1 antagonist, on cardiac function, myofibrillar and myosin ATPase activity as well as myosin heavy chain (MHC) isozyme expression in diabetic hearts. Diabetes was induced in rats by a single injection of streptozotocin (65 mg/kg; i.v.) and these animals were treated with and without enalapril (10 mg/kg/day; oral) or losartan (20 mg/kg/day; oral) for 8 weeks. Enalapril or losartan prevented the depressions in left ventricular rate of pressure development, rate of pressure decay and ventricular weight seen in diabetic animals. Both drugs also attenuated the decrease in myofibrillar Ca2+-ATPase, Mg2+-ATPase and myosin ATPase activity seen in diabetic rats. The diabetes-induced increase in beta-MHC content and gene expression as well as the decrease in alpha-MHC content and mRNA levels were also prevented by enalapril and losartan. These results suggest the occurrence of myofibrillar remodelling in diabetic cardiomyopathy and provide evidence that the beneficial effects of RAS blockade in diabetes may be associated with attenuation of myofibrillar remodelling in the heart.
Mol Cell Biochem 2004 Jun
PMID:Renin-angiotensin blockade attenuates cardiac myofibrillar remodelling in chronic diabetes. 1536 13

Skeletal muscles consist of slow-twitch and fast-twitch muscle fibers, which have distinct physiological and biochemical properties. The muscle fiber composition determines the contractile velocity and fatigability of a particular skeletal muscle. We analyzed the systemic distribution of slow muscle fibers in all rodent skeletal muscles by myosin ATPase staining and found that only seven hindlimb skeletal muscles were extremely rich in slow muscle fibers. These included the mouse piriformis (56.5%), gluteus minimus (35.7%), vastus intermedius (24.7%), quadratus femoris (69.9%), adductor brevis (44.3%), gracilis (24.6%), and soleus muscles (35.1%). In mice, the relative proportion of slow muscle fibers did not exceed 15% in skeletal muscles in other regions. The distribution of slow muscle fibers was well conserved in rats and rabbits. The soleus muscle is an important antigravity muscle in both rodents and humans; therefore, these skeletal muscles rich in slow muscle fibers might play an important role in sustaining neutral alignment of the lower extremity.
Comp Biochem Physiol B Biochem Mol Biol 2005 Jan
PMID:Seven skeletal muscles rich in slow muscle fibers may function to sustain neutral position in the rodent hindlimb. 1562 8

Previous short-term studies have correlated an increase in the phosphorylation of the 20-kDa light chain of myosin II (MLC20) with blebbing in apoptotic cells. We have found that this increase in MLC20 phosphorylation is rapidly followed by MLC20 dephosphorylation when cells are stimulated with various apoptotic agents. MLC20 dephosphorylation is not a consequence of apoptosis because MLC20 dephosphorylation precedes caspase activation when cells are stimulated with a proapoptotic agent or when myosin light chain kinase (MLCK) is inhibited pharmacologically or by microinjecting an inhibitory antibody to MLCK. Moreover, blocking caspase activation increased cell survival when MLCK is inhibited or when cells are treated with tumor necrosis factor alpha. Depolymerizing actin filaments or detaching cells, processes that destabilize the cytoskeleton, or inhibiting myosin ATPase activity also resulted in MLC20 dephosphorylation and cell death. In vivo experiments showed that inhibiting MLCK increased the number of apoptotic cells and retarded the growth of mammary cancer cells in mice. Thus, MLC20 dephosphorylation occurs during physiological cell death and prolonged MLC20 dephosphorylation can trigger apoptosis.
Mol Cell Biol 2005 Jul
PMID:Inhibiting myosin light chain kinase induces apoptosis in vitro and in vivo. 1598 34

In Drosophila melanogaster expression of muscle myosin heavy chain isoforms occurs by alternative splicing of transcripts from a single gene. The exon 7 domain is one of four variable regions in the catalytic head and is located near the nucleotide-binding site. To ascribe a functional role to this domain, we created two chimeric myosin isoforms (indirect flight isoform-exon 7a and embryonic-exon 7d) that differ from the native indirect flight muscle and embryonic body-wall muscle isoforms only in the exon 7 region. Germline transformation and subsequent expression of the chimeric myosins in the indirect flight muscle of myosin-null Drosophila allowed us to purify the myosin for in vitro studies and to assess in vivo structure and function of transgenic muscles. Intriguingly, in vitro experiments show the exon 7 domain modulates myosin ATPase activity but has no effect on actin filament velocity, a novel result compared to similar studies with other Drosophila variable exons. Transgenic flies expressing the indirect flight isoform-exon 7a have normal indirect flight muscle structure, and flight and jump ability. However, expression of the embryonic-exon 7d chimeric isoform yields flightless flies that show improvements in both the structural stability of the indirect flight muscle and in locomotor abilities as compared to flies expressing the embryonic isoform. Overall, our results suggest the exon 7 domain participates in the regulation of the attachment of myosin to actin in order to fine-tune the physiological properties of Drosophila myosin isoforms.
J Mol Biol 2005 Oct 14
PMID:An alternative domain near the nucleotide-binding site of Drosophila muscle myosin affects ATPase kinetics. 1615 86

We have used site-directed spin and fluorescence labeling to test molecular models of the actin-myosin interface. Force is generated when the actin-myosin complex undergoes a transition from a disordered weak-binding state to an ordered strong-binding state. Actomyosin interface models, in which residues are classified as contributing to either weak or strong binding, have been derived by fitting individual crystallographic structures of actin and myosin into actomyosin cryo-EM maps. Our goal is to test these models using site-directed spectroscopic probes on actin and myosin. Starting with Cys-lite constructs of both yeast actin (ActC) and the Dictyostelium myosin II motor domain (S1dC), site-directed labeling (SDL) mutants were generated by mutating residues to Cys in the proposed weak and strong-binding interfaces. This report focuses on the effects of forming the strong-binding complex on four SDL mutants, two located in the proposed weak-binding interface (ActC5 and S1dC619) and two located in the proposed strong-binding interface (ActC345 and S1dC401). Neither the mutations nor labeling prevented strong actomyosin binding or actin-activation of myosin ATPase. Formation of the strong-binding complex resulted in decreased spin and fluorescence probe mobility at all sites, but both myosin-bound probes showed remarkably high mobility even after complex formation. Complex formation decreased solvent accessibility for both actin-bound probes, but increased it for the myosin-bound probes. These results are not consistent with a simple model in which there are discrete weak and strong interfaces, with only the strong interface forming under strong-binding conditions, nor are they consistent with a model in which surface residues become rigid and inaccessible upon complex formation. We conclude that all four of these residues are involved in the strong actin-myosin interface, but this interface is remarkably dynamic, especially on the surface of myosin.
J Mol Biol 2006 Mar 10
PMID:Structural dynamics of the actin-myosin interface by site-directed spectroscopy. 1640 6

Here, we provide functional and direct structural evidence that alphaB-crystallin, a member of the small heat-shock protein family, suppresses thermal unfolding and aggregation of the myosin II molecular motor. Chicken skeletal muscle myosin was thermally unfolded at heat-shock temperature (43 degrees C) in the absence and in the presence of alphaB-crystallin. The ATPase activity of myosin at 25 degrees C was used as a parameter to monitor its unfolding. Myosin retained only 65% and 8% of its ATPase activity when incubated at heat-shock temperature for 15 min and 30 min, respectively. However, 84% and 58% of the myosin ATPase activity was maintained when it was incubated with alphaB-crystallin under the same conditions. Furthermore, actin-stimulated ATPase activity of myosin was reduced by approximately 90%, when myosin was thermally unfolded at 43 degrees C for 30 min, but was reduced by only approximately 42% when it was incubated with alphaB-crystallin under the same conditions. Light-scattering assays and bound thioflavin T fluorescence indicated that myosin aggregates when incubated at 43 degrees C for 30 min, while alphaB-crystallin suppressed this thermal aggregation. Photo-labeled bis-ANS alphaB-crystallin fluorescence studies confirmed the transient interaction of alphaB-crystallin with myosin. These findings were further supported by electron microscopy of rotary shadowed molecules. This revealed that approximately 94% of myosin molecules formed inter and intra-molecular aggregates when incubated at 43 degrees C for 30 min. alphaB-Crystallin, however, protected approximately 48% of the myosin molecules from thermal aggregation, with protected myosin appearing identical to unheated molecules. These results are the first to show that alphaB-crystallin maintains myosin enzymatic activity and prevents the aggregation of the motor under heat-shock conditions. Thus, alphaB-crystallin may be critical for nascent myosin folding, promoting myofibrillogenesis, maintaining cytoskeletal integrity and sustaining muscle performance, since heat-shock temperatures can be produced during multiple stress conditions or vigorous exercise.
J Mol Biol 2006 May 05
PMID:alphaB-crystallin maintains skeletal muscle myosin enzymatic activity and prevents its aggregation under heat-shock stress. 1654 10

Ookinetes of the genus Plasmodium are motile, invasive cells that develop in the mosquito midgut following ingestion of a parasite-infected blood meal. We show here that ookinetes display gliding motility on glass slides in the presence of insect cells. Moreover, in addition to stationary "flexing" and "twirling" of the cells, two distinct types of movements occur: productive forward translocational motility in straight segment that progresses with an average speed of approximately 6mum/min and rotational motility, which does not lead to forward translocation. Locomotion is reduced by treatment with butanedione monoxime, an inhibitor of myosin ATPase, and by three different actin inhibitors. We also studied the expression during ookinete development of genes encoding actin and two small class XIV myosins, PbMyoA, and PbMyoB. Western immunoblots revealed that PbMyoA is only present in fully mature ookinetes, whilst the other two proteins are additionally expressed in gametocytes and zygotes. Immunofluorescence experiments reveal that MyoA and actin co-localize in the apical tip of the parasite whereas MyoB displays a punctate pattern of expression around the entire cell periphery. Following treatment with jasplakinolide, the apparent level of detectable actin appears to substantially increase and becomes concentrated in a discrete area in the basal pole of the ookinete.
Mol Biochem Parasitol 2006 Dec
PMID:Involvement of actin and myosins in Plasmodium berghei ookinete motility. 1702 9

Epithelial-mesenchymal-myofibroblast transition (EMT), a key feature in organ fibrosis, is regulated by the state of intercellular contacts. Our recent studies have shown that an initial injury of cell-cell junctions is a prerequisite for transforming growth factor-beta1 (TGF-beta1)-induced transdifferentiation of kidney tubular cells into alpha-smooth muscle actin (SMA)-expressing myofibroblasts. Here we analyzed the underlying contact-dependent mechanisms. Ca(2+) removal-induced disruption of intercellular junctions provoked Rho/Rho kinase (ROK)-mediated myosin light chain (MLC) phosphorylation and Rho/ROK-dependent SMA promoter activation. Importantly, myosin-based contractility itself played a causal role, because the myosin ATPase inhibitor blebbistatin or a nonphosphorylatable, dominant negative MLC (DN-MLC) abolished the contact disruption-triggered SMA promoter activation, eliminated the synergy between contact injury and TGF-beta1, and suppressed SMA expression. To explore the responsible mechanisms, we investigated the localization of the main SMA-inducing transcription factors, serum response factor (SRF), and its coactivator myocardin-related transcription factor (MRTF). Contact injury enhanced nuclear accumulation of SRF and MRTF. These processes were inhibited by DN-Rho or DN-MLC. TGF-beta1 strongly facilitated nuclear accumulation of MRTF in cells with reduced contacts but not in intact epithelia. DN-myocardin abrogated the Ca(2+)-removal- +/- TGF-beta1-induced promoter activation. These studies define a new mechanism whereby cell contacts regulate epithelial-myofibroblast transition via Rho-ROK-phospho-MLC-dependent nuclear accumulation of MRTF.
Mol Biol Cell 2007 Mar
PMID:Cell contact-dependent regulation of epithelial-myofibroblast transition via the rho-rho kinase-phospho-myosin pathway. 2279 86

Muscle contraction is driven by a cycle of conformational changes in the myosin II head. After myosin binds ATP and releases from the actin fibril, myosin prepares for the next power stroke by rotating back the converter domain that carries the lever arm by 60 degrees . This recovery stroke is coupled to the activation of myosin ATPase by a mechanism that is essential for an efficient motor cycle. The mechanics of this coupling have been proposed to occur via two distinct and successive motions of the two helices that hold the converter domain: in a first phase a seesaw motion of the relay helix, followed by a piston-like motion of the SH1 helix in a second phase. To test this model, we have determined the principal motions of these structural elements during equilibrium molecular dynamics simulations of the crystallographic end states of the recovery-stroke by using principal component analysis. This reveals that the only principal motions of these two helices that make a large-amplitude contribution towards the conformational change of the recovery stroke are indeed the predicted seesaw and piston motions. Moreover, the results demonstrate that the seesaw motion of the relay helix dominates in the dynamics of the pre-recovery stroke structure, but not in the dynamics of the post-recovery stroke structure, and vice versa for the piston motion of the SH1 helix. This is consistent with the order of the proposed two-phase model for the coupling mechanism of the recovery stroke. Molecular movies of these principal motions are available at http://www.iwr.uni-heidelberg.de/groups/biocomp/fischer.
J Mol Biol 2007 Mar 23
PMID:The principal motions involved in the coupling mechanism of the recovery stroke of the myosin motor. 1727 22


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