Actin Preparations Research Articles

Understanding the Role of Filamentous Actin in Food Quality: From Structure to Application.

Actin, a multifunctional protein highly expressed in eukaryotes, is widely distributed throughout cells and serves as a crucial component of the cytoskeleton. Its presence is integral to maintaining cell morphology and participating in various biological processes. As an irreplaceable component of myofibrillar proteins, actin, including G-actin and F-actin, is highly related to food quality. Up to now, purification of actin at a moderate level remains to be overcome. In this paper, we have reviewed the structures and functions of actin, the methods to obtain actin, and the relationships between actin and food texture, color, and flavor. Moreover, actin finds applications in diverse fields such as food safety, bioengineering, and nanomaterials. Developing an actin preparation method at the industrial level will help promote its further applications in food science, nutrition, and safety.

ANALISIS PUTUSAN PENGADILAN NEGERI GORONTALO NOMOR 209/PID.SUS/2021 BERKAITAN DENGAN TINDAK PIDANA NARKOTIKA YANG DILAKUKAN DENGAN PEMUFAKATAN JAHAT

In providing health services, narcotics have an important role because they are used for medical and research purposes, so their availability needs to be guaranteed through production and import activities. Evil conspiracy is an act of preparation. Many law enforcement officers in Indonesia apply Article 132 paragraph 1. For example, two people have been arrested and charged for purchasing, carrying and subsequently using these narcotics. This research aims to analyze the judge's decision regarding criminal acts involving malicious conspiracy. The approach method uses primary data by conducting observations and interviews with related parties. Based on the facts, the author concludes: Narcotics crime with malicious intent because the defendant when committing the act was in good physical and mental health and there was no reason to expunge the crime and fulfilled the elements in Article 114 paragraph 2 of Law Number 35 of 2009 concerning Narcotics and Judges imposed a prison sentence of 8 years and a fine of IDR 2,000,000,000.00, with the provision that if the fine is not paid it will be replaced by a prison sentence of 3 months

α-actinin accounts for the bioactivity of actin preparations in inducing STAT target genes in Drosophila melanogaster.

Damage-associated molecular patterns (DAMPs) are molecules exposed or released by dead cells that trigger or modulate immunity and tissue repair. In vertebrates, the cytoskeletal component F-actin is a DAMP specifically recognised by DNGR-1, an innate immune receptor. Previously we suggested that actin is also a DAMP in Drosophila melanogaster by inducing STAT-dependent genes (<xref ref-type="bibr" rid="bib10">Srinivasan et al., 2016</xref>). Here, we revise that conclusion and report that α-actinin is far more potent than actin at inducing the same STAT response and can be found in trace amounts in actin preparations. Recombinant expression of actin or α-actinin in bacteria demonstrated that only α-actinin could drive the expression of STAT target genes in Drosophila. The response to injected α-actinin required the same signalling cascade that we had identified in our previous work using actin preparations. Taken together, these data indicate that α-actinin rather than actin drives STAT activation when injected into Drosophila.

Production of Human β-Actin Using a Bacterial Expression System with a Cold Shock Vector.

Actin is one of the most abundant proteins in the cytoplasm of eukaryotic cells and plays important roles in a variety of cellular functions. However, it has been difficult to produce actin in substantial amounts using bacterial expression systems. In this article, a new method is described for the production of recombinant actin in bacterial cells. Human β-actin (His-tagged) can be expressed using a cold shock vector, pCold, in a bacterial expression system and then separated with a Ni-chelating resin, followed by a polymerization/depolymerization cycle or column chromatography with the Ni-chelating resin. The purified recombinant β-actin shows normal polymerization ability compared with commercially available β-actin purified from human platelets. This article also describes the preparation of mutant actin(G168R). This purified mutant exhibits impaired polymerization ability. The system and procedures described here will provide a useful method for the production of actin isoforms and their mutants. © 2018 by John Wiley & Sons, Inc.

Natural Actin and Tropomyosin from Molluscan Catch Muscle

In this work, the main proteins of thin filaments (actin and tropomyosin) were isolated from the catch muscle of the mussel Crenomytilus grayanus and the rabbit skeletal muscles. Rabbit actin and tropomyosin and mussel tropomyosin were isolated by traditional methods as opposed to natural mussel actin (isolation of the mussel actin from acetone powder is impossible). These proteins were used to reconstruct actin+tropomyosin complexes in nonhybrid and hybrid manner. A non-hybrid complex, reconstructed from rabbit actin and tropomyosin, has higher reduced viscosity than complex of mussel proteins where reduced viscosity was nearly indistinguishable from the intrinsic viscosity. ÐÂ’oth rabbit and mussel actin were purified by polymerization-repolymerization cycles followed by gel filtration chromatography. During purification, the viscosity of both actins increased, and the difference in viscosity between them decreased. Based on the SDS-electrophoresis, we did not find any of the other proteins in the chromatographic fractions, except actin. However, obtained chromatographic fractions have significant differences in viscosity and rate of polymerization. We believe that these properties caused by the presence of an ending factor” (such as β-actinin or Cap Z) in actin preparations. The data obtained indicate that isolation of “natural” actin is accompanied by a coextraction of an unknown or known ending factor in amounts that may be greater than those obtained from the acetone powder of rabbit skeletal muscles.

Nerve pathologic features differentiate POEMS syndrome from CIDP.

The objective of this study is to determine if the nerve pathology in patients with POEMS syndrome is different from CIDP. We hypothesized that nerve biopsies from patients with POEMS syndrome would have more small vessels and axonal degeneration but less inflammation than CIDP.We performed a retrospective analysis of nerve biopsies performed on “classic” CIDP and POEMS cases. Nerve biopsies were blinded and reviewed by two of the authors (EAP, PJBD). Teased fibers, paraffin-embedded sections, semithin sections and immunostains were analyzed. Small endoneurial and epineurial vessels were counted on paraffin sections with smooth muscle actin (SMACTIN) preparation to judge for neovascularization.A total of 61 cases (35-POEMS, 26-CIDP) were included. The POEMS-group had significantly higher axonal degeneration and fewer normal myelinated fibers on teased fiber preparations. The CIDP-group had significantly more endoneurial mononuclear inflammation on paraffin sections and immunostains. Large onion-bulbs were present only in CIDP cases. A significantly higher number of epineurial vessels was present in POEMS biopsies, with a total count of 120 epineurial vessels predicted as best cutoff to differentiate both conditions (77 % specific and 54 % sensitive).In conclusion, nerve biopsy can be helpful in distinguishing POEMS syndrome from CIDP. POEMS syndrome demonstrates more axonal degeneration and epineurial neovascularization whereas CIDP has greater endoneurial inflammation and onion-bulb formation. These findings support the idea that there are differing underlying mechanisms for these disorders, POEMS being related to paraneoplastic vasculopathy associated with angiogenic factors and CIDP related to inflammatory demyelination.

The development of “modern” palaeontological laboratory methods: a century of progress

ABSTRACTVertebrate fossils have been converted from natural history objects into research specimens through the act of preparation for over 200 years. All of the basic techniques applied to specimens in the 21st Century were already in use in palaeontological laboratories by the first decade of the 1900s. It behoves any worker in the field to be intimately familiar with processes for treatment of specimens, as these procedures almost always permanently alter material available for interpretation. Historic treatments also complicate attempts to re-treat or re-prepare specimens. Sometimes this results in damage to fossils and loss of information, and often in wasted resources. Most palaeontologists are unaware of the historical evolution of laboratory methods through this time; much of the documentation of this process is considered to be obscure. However, there is in fact a robust body of literature that chronicles the development of procedures for the preparation of fossils. Awareness of the past development of methods is crucial to guiding future directions in the palaeontological laboratory. Regular reporting of laboratory methods in the technical literature at a pace matching that of other analytical methods is integral to the function of palaeontology as a science.

남북한 수산제도의 비교연구

For establishment of post-Unification fisheries program, this research has opened a fisheries Act system for South and North Korea and searched a policy direction to make new Fisheries Act for future South and North Korean fisheries program. In addition, North Korea's present fishery industry must be accurately understood and acknowledge in its point of issues in order to develop and improve to rational direction and to overcome the present South and North's fishery industry. As a level to prepare for future unification, reform and reaction of long-termed and well organized South and North's fisheries program must be arranged. Consequently, fishing permits of South and North, licensing system, fisheries resource management system, fisheries adjustment system, foreign fishing regulations system will be compared in this research, and also find an improvement on North Korea's fisheries related act in preparation of future unification.

Preparation of States in Open Quantum Mechanics

We study preparation of states for open quantum mechanics. For non-Markovian systems that are initially correlated with the environment, the effects of the preparation procedure are nontrivial. This is due to the indirect effects on the state of the environment induced via the correlations with the system and the act of preparation on the system. We give three concrete examples of preparation procedure to elucidate our claims.

Mutation of Actin Tyr-53 Alters the Conformations of the DNase I-binding Loop and the Nucleotide-binding Cleft

All but 11 of the 323 known actin sequences have Tyr at position 53, and the 11 exceptions have the conservative substitution Phe, which raises the following questions. What is the critical role(s) of Tyr-53, and, if it can be replaced by Phe, why has this happened so infrequently? We compared the properties of purified endogenous Dictyostelium actin and mutant constructs with Tyr-53 replaced by Phe, Ala, Glu, Trp, and Leu. The Y53F mutant did not differ significantly from endogenous actin in any of the properties assayed, but the Y53A and Y53E mutants differed substantially; affinity for DNase I was reduced, the rate of nucleotide exchange was increased, the critical concentration for polymerization was increased, filament elongation was inhibited, and polymerized actin was in the form of small oligomers and imperfect filaments. Growth and/or development of cells expressing these actin mutants were also inhibited. The Trp and Leu mutations had lesser but still significant effects on cell phenotype and the biochemical properties of the purified actins. We conclude that either Tyr or Phe is required to maintain the functional conformations of the DNase I-binding loop (D-loop) in both G- and F-actin, and that the conformation of the D-loop affects not only the properties that directly involve the D-loop (binding to DNase I and polymerization) but also allosterically modifies the conformation of the nucleotide-binding cleft, thus increasing the rate of nucleotide exchange. The apparent evolutionary "preference" for Tyr at position 53 may be the result of Tyr allowing dynamic modification of the D-loop conformation by phosphorylation (Baek, K., Liu, X., Ferron, F., Shu, S., Korn, E. D., and Dominguez, R. (2008) Proc. Natl. Acad. Sci. U.S.A. 105, 11748-11753) with effects similar, but not identical, to those of the Ala and Glu mutations.

Differential Regulation of Actin Polymerization and Structure by Yeast Formin Isoforms

The budding yeast formins, Bnr1 and Bni1, behave very differently with respect to their interactions with muscle actin. However, the mechanisms underlying these differences are unclear, and these formins do not interact with muscle actin in vivo. We use yeast wild type and mutant actins to further assess these differences between Bnr1 and Bni1. Low ionic strength G-buffer does not promote actin polymerization. However, Bnr1, but not Bni1, causes the polymerization of pyrene-labeled Mg-G-actin in G-buffer into single filaments based on fluorometric and EM observations. Polymerization by Bnr1 does not occur with Ca-G-actin. By cosedimentation, maximum filament formation occurs at a Bnr1:actin ratio of 1:2. The interaction of Bnr1 with pyrene-labeled S265C Mg-actin yields a pyrene excimer peak, from the cross-strand interaction of pyrene probes, which only occurs in the context of F-actin. In F-buffer, Bnr1 promotes much faster yeast actin polymerization than Bni1. It also bundles the F-actin in contrast to the low ionic strength situation where only single filaments form. Thus, the differences previously observed with muscle actin are not actin isoform-specific. The binding of both formins to F-actin saturate at an equimolar ratio, but only about 30% of each formin cosediments with F-actin. Finally, addition of Bnr1 but not Bni1 to pyrene-labeled wild type and S265C Mg-F actins enhanced the pyrene- and pyrene-excimer fluorescence, respectively, suggesting Bnr1 also alters F-actin structure. These differences may facilitate the ability of Bnr1 to form the actin cables needed for polarized delivery of nutrients and organelles to the growing yeast bud.

Critical evaluation of the use of bioinformatics as a theoretical tool to find high-potential sources of ACE inhibitory peptides

A bioinformatics analysis to screen for high-potential sources of angiotensin converting enzyme (ACE) inhibitory peptides was conducted in the area of insect muscle proteins. Vertebrate muscle proteins are reported as good sources of ACE inhibitory peptides, while the research on invertebrate muscle proteins is limited. A phylogenetic tree constructed with actin sequences of both vertebrate and invertebrate species indicated a high homology. Furthermore, a quantitative in silico ACE inhibition analysis suggested that actin proteins of invertebrates have potentials as new sources of ACE inhibitory peptides. On one insect, Bombyx mori, a more detailed in silico analysis was done followed by a small experimental study. The in silico analysis indicated B. mori as a high-potential source of ACE inhibitory peptides and this was supported by the ACE inhibitory activity of the partially purified actin preparation. In conclusion, in food science, in silico analysis can be used as fast initial screening tool to look for high-potential sources of ACE inhibitory peptides and other peptidic bioactivities.

The Slow Skeletal Muscle Isoform of Myosin Shows Kinetic Features Common to Smooth and Non-muscle Myosins

Fast and slow mammalian muscle myosins differ in the heavy chain sequences (MHC-2, MHC-1) and muscles expressing the two isoforms contract at markedly different velocities. One role of slow skeletal muscles is to maintain posture with low ATP turnover, and MHC-1 expressed in these muscles is identical to heavy chain of the beta-myosin of cardiac muscle. Few studies have addressed the biochemical kinetic properties of the slow MHC-1 isoform. We report here a detailed analysis of the MHC-1 isoform of the rabbit compared with MHC-2 and focus on the mechanism of ADP release. We show that MHC-1, like some non-muscle myosins, shows a biphasic dissociation of actin-myosin by ATP. Most of the actin-myosin dissociates at up to approximately 1000 s(-1), a very similar rate constant to MHC-2, but 10-15% of the complex must go through a slow isomerization (approximately 20 s(-1)) before ATP can dissociate it. Similar slow isomerizations were seen in the displacement of ADP from actin-myosin.ADP and provide evidence of three closely related actin-myosin.ADP complexes, a complex in rapid equilibrium with free ADP, a complex from which ADP is released at the rate required to define the maximum shortening velocity of slow muscle fibers (approximately 20 s(-1)), and a third complex that releases ADP too slowly (approximately 6 s(-1)) to be on the main ATPase pathway. The role of these actin-myosin.ADP complexes in the mechanochemistry of slow muscle contraction is discussed in relation to the load dependence of ADP release.

Morphofunctional effects of applications of glutamate and dopamine on the goldfish Mauthner neurons

In the goldfish, we studied the effects of intramedullar applications of glutamate (Glu), dopamine (DA), and of long-lasting rotational stimulation on the functional activity, dimensional characteristics, and ultrastructure of Mauthner neurons (MNs). Applications of Glu, especially when combined with rotational stimulation, were found to result in suppression of the function of MNs, in a decrease in their dimensions and lengths of desmosome-like contacts (DLCs, whose structure is determined by filamentous actin) in afferent mixed and chemical synapses, and in destruction of actin microfilaments in the cytoskeleton of MNs. Applications of DA, vice versa, induced an increase in the resistance to the effects of long-lasting stimulation and stabilized the dimensions of MNs; the length of DLCs increased in afferent synapses of both the above types, and the number of fibrillar actin bridges in the DLC cleft of mixed synapses also increased. Bundles of the actin filaments, which were preserved after stimulation, appeared in the cytoskeleton of MNs. Testing of the action of neurotransmitters on actin preparations in vitro showed that Glu entirely depolymerizes filamentous actin, while DA, vice versa, polymerizes monomeric actin. Thus, the Glu-and DA-induced reactions are similar in their types and are of a reciprocal nature both in the actin cytoskeleton of MNs in situ and in purified actin in vitro; these effects correlate with suppression of the functional state of MNs under the influence of Glu and with stabilization of this state under the influence of DA. These results agree with the concept on the roles of depolymerization and polymerization of actin in changes of the morphofunctional state of MNs and show that actin of the cytoskeleton of MNs is a cellular target for the actions of Glu and DA. The similarity between the effects of tested neurotransmitters on actin in MNs in situ and in cell-free preparations in vitro allows us to hypothesize that these transmitters can penetrate into the neuron.

Effects of Human Deafness γ-Actin Mutations (DFNA20/26) on Actin Function

Six point mutations in non-muscle gamma-actin at the DFNA20/26 locus cause autosomal dominant nonsyndromic hearing loss. The molecular basis for the hearing loss is unknown. We have engineered each gamma-actin mutation into yeast actin to investigate the effects of these mutations on actin function in vivo and in vitro. Cells expressing each of the mutant actins as the sole actin in the cell were viable. Four of the six mutant strains exhibited significant growth deficiencies in complete medium and an inability to grow on glycerol as the sole carbon source, implying a mitochondrial defect(s). These four strains exhibited abnormal mitochondrial morphology, although the mtDNA was retained. All of the mutant cells exhibited an abnormally high percentage of fragmented/non-polarized actin cables or randomly distributed actin patches. Five of the six mutants displayed strain-specific vacuole morphological abnormalities. Two of the purified mutant actins exhibited decreased thermal stability and increased rates of nucleotide exchange, indicative of increased protein flexibility. V370A actin alone polymerized abnormally. It aggregated in low ionic strength buffer and polymerized faster than wild-type actin, probably in part because of enhanced nucleation. Mixtures of wild-type and V370A actins displayed kinetic properties in proportion to the mole fraction of each actin in the mixture. No dominant effect of the mutant actin was observed. Our results suggest that a major factor in the deafness caused by these mutations is an altered ability of the actin filaments to be properly regulated by actin-binding proteins rather than an inability to polymerize.

Processivity of Chimeric Class V Myosins

Unconventional myosin V takes many 36-nm steps along an actin filament before it dissociates, thus ensuring its ability to move cargo intracellularly over long distances. In the present study we assessed the structural features that affect processive run length by analyzing the properties of chimeras of mouse myosin V and a non-processive class V myosin from yeast (Myo4p) (Reck-Peterson, S. L., Tyska, M. J., Novick, P. J., and Mooseker, M. S. (2001) J. Cell Biol. 153, 1121-1126). Surprisingly a chimera containing the yeast motor domain on the neck and rod of mouse myosin V (Y-MD) showed longer run lengths than mouse wild type at low salt. Run lengths of mouse myosin V showed little salt dependence, whereas those of Y-MD decreased steeply with ionic strength, similar to a chimera containing yeast loop 2 in the mouse myosin V backbone. Loop 2 binds to acidic patches on actin in the weak binding states of the cycle (Volkmann, N., Liu, H., Hazelwood, L., Krementsova, E. B., Lowey, S., Trybus, K. M., and Hanein, D. (2005) Mol. Cell 19, 595-605). Constructs containing yeast loop 2, which has no net charge compared with +6 for wild type, showed a higher K(m) for actin in steady-state ATPase assays. The results imply that a positively charged loop 2 and a high affinity for actin are important to maintain processivity near physiologic ionic strength.

Cooperative inhibition of actin filaments in the absence of tropomyosin.

We measured the inhibition of actin activated myosin subfragment-1 MgATPase activity in a solution containing no added KCl (5 mM PIPES.K2 (pH 7.1), 2.5 mM MgCl2, 1 mM DTT, 1 mM NaN3, 5 mM MgATP). Maximal inhibition was observed with substoichiometric concentrations of caldesmon, caldesmon domain 4, troponin and troponin I. In six experiments using different preparations of actin, S-1 and caldesmon 50% inhibition required 0.09 +/- 0.01 (sem) caldesmon added per actin. This compares with 0.66 +/- 0.32 (sem, n = 5) caldesmon per actin for 50% inhibition in the presence of 60 mM KCl. With caldesmon domain 4, 50% inhibition was achieved with 0.17 +/- 0.08 (n = 11) domain 4 added per actin. We measured the amount of caldesmon bound at the same time as inhibition. Complete inhibition of actin activated ATPase needed only one caldesmon bound per 5.0 +/- 0.5 (sem, n = 5) actin monomers or one caldesmon domain 4 bound per 3.9 +/- 0.6 (sem, n = 3) actin monomers at zero KCl. We conclude that under these conditions inhibition of actin is cooperative despite the absence of tropomyosin. We measured the effect of caldesmon inhibition upon S-1 binding to actin. S-1.ADP.Pi (weak binding) was not affected by caldesmon concentrations giving 80% inhibition, however S-1.ADP (strong binding) was highly cooperative, being very weak at <0.3 microM but indistinguishable from uninhibited actin at >2 microM S-1.ADP. We conclude that actin can exist in two activity states corresponding to the 'on' and 'off' states of actin-tropomyosin and inhibitory proteins function as allosteric-cooperative inhibitors of actin. The implications of these findings for the role of tropomyosin in thin filament regulation are discussed.

Cross-linked dimers with nucleating activity in actin prepared from muscle acetone powder.

A covalently linked actin dimer is identified in solutions of actin prepared from an acetone powder from skeletal muscle. This actin dimer acts as an actin nucleating factor (ANF), decreasing the half-time for spontaneous actin polymerization. ANF reacts with antibodies to both the N- and C-terminal portions of actin on Western blots and migrates during reduced polyacrylamide gel electrophoresis like actin cross-linked with N, N'-p-phenylenebismaleimide. The origin of the cross-linked dimer appears to be related to the presence of carbonyl groups in purified actin. A large number of carbonyls (approximately 0.3/actin) are introduced into actin during the prolonged treatment with acetone in the preparation of the muscle acetone powder from which actin is extracted. Actin extracted from acetone powder prepared by a single acetone wash and actin prepared from bovine spleen, which is not washed with acetone, both contain fewer carbonyl groups (approximately 0.05 carbonyl/actin). ANF forms spontaneously in solutions of polymer actin containing 0.3 carbonyl/actin. We speculate that a reaction between a carbonyl on one actin polymer subunit and a lysine on a neighboring subunit is responsible for ANF formation. The presence of cross-linked actin dimers in commonly used skeletal muscle actin preparations could certainly affect studies of actin polymerization and, particularly, studies of the nucleation reaction. The physiological relevance of ANF is not clear, but given the large cellular concentration of actin, similar reactions yielding ANF could occur in vivo when increased levels of reactive oxygen species are present.

Actin Residue Glu93 Is Identified as an Amino Acid Affecting Myosin Binding

Many mutants have been described that affect the function of the actin encoded by the Drosophila melanogaster indirect flight muscle-specific actin gene, Act88F. We describe the development of procedures for purification of this actin from the other isoforms expressed in the fly as well as in vitro motility, single molecule force/displacement measurements, and stop-flow solution kinetic studies of the wild-type actin and that of the E93K mutation of the Act88F gene. We show that this mutation affects in vitro motility of F-actin, in both the presence and absence of methylcellulose, and the ability of the ACT88F actin to bind the S1 fragment of rabbit skeletal myosin. However, optical tweezer measurements of the actomyosin working stroke and the force transmitted from the rabbit heavy meromyosin to and through F-actin are unchanged by the mutation. These results support the proposal (Holmes, K. C. (1995) Biophys J. 68, (suppl.) 2-7) that actin residue Glu(93) is part of the secondary myosin binding site and suggest that myosin binding occurs first at the primary myosin binding site and then at the secondary site.

Intrastrand cross-linked actin between Gln-41 and Cys-374. III. Inhibition of motion and force generation with myosin.

Structural and functional properties of intrastrand, ANP (N-(4-azido-2-nitrophenyl)-putrescine) cross-linked actin filaments, between Gln-41 and Cys-374 on adjacent monomers, were examined for several preparations of such actin. Extensively cross-linked F-actin (with 12% un-cross-linked monomers) lost at 60 degrees C the ability to activate myosin ATPase at a 100-fold slower rate and unfolded in CD melting experiments at a temperature higher by 11 degrees C than the un-cross-linked actin. Electron microscopy and image reconstruction of these filaments did not reveal any gross changes in F-actin structure but showed a change in the orientation of subdomain 2 and a decrease in interstrand connectivity. Rigor and weak (in the presence of ATP) myosin subfragment (S1) binding and acto-S1 ATPase did not show major changes upon 50% and 90% ANP cross-linking of F-actin; the Kd and Km values were little affected by the cross-linking, and the Vmax decreased by 50% for the extensively cross-linked actin. The cross-linking of actin (50%) decreased the mean speed and the number of sliding filaments in the in vitro motility assays by approximately 35% while the relative force, as measured by using external load in these assays, was inhibited by approximately 25%. The mean speed of actin filaments decreased with the increase in their cross-linking and approached 0 for the 90% cross-linked actin. Also examined were actin filaments reassembled from cross-linked and purified ANP cross-linked dimers, trimers, and oligomers. All of these filaments had the same acto-S1 ATPase and rigor S1 binding properties but different behavior in the in vitro motility assays. Filaments made of cross-linked dimers moved at approximately 50% of the speed of the un-cross-linked actin. The movement of filaments made of cross-linked trimers was inhibited more severely, and the oligomer-made filaments did not move at all. These results show the uncoupling between force generation and other events in actomyosin interactions and emphasize the role of actin filament structure and dynamics in the contractile process.