Cross-linking constraints on F-actin structure 1 1Edited by M. F. Moody

Kim, Eldar; Wriggers, Willy; Phillips, Martin; Kokabi, Kevin; Rubenstein, Peter A.; Reisler, Emil

doi:10.1006/jmbi.2000.3727

Cited by 61 publications

(71 citation statements)

References 36 publications

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“…An intermolecular pathway of communication between the DNase-I binding loop and myosin binding sites is consistent with the fact that activation of myosin ATPase requires actin in its polymer form, with a prediction from F-actin models that this loop interacts with subdomains 1 and 3 of an adjacent F-actin subunit along the same long pitch helical strand (26,66,67), and with biochemical evidence for its intermolecular interaction with the C terminus in subdomain 1 of actin (27,68,69). However, the dramatic enhancement of the turnover rate of F-actin subunits in ECP-cleaved F-actin, contrasting with a small effect of subtilisin cleavage (36), argue for participation of only the N-terminal part of the DNase-I binding loop, encompassing ECP cleavage but not subtilisin cleavage site, in the intersubunit interactions as predicted in the F-actin model of Holmes et al (26).…”

Section: Discussionsupporting

confidence: 80%

“…It is plausible that changes in the arrangement of these structural elements are mutually related. The N-terminal segment of the DNase-I binding loop and Phe 262 to Ile 274 loop, along with the C terminus of actin, form a common interface between three adjacent F-actin subunits (26,27,72). Conformational coupling between the N-terminal segment of the DNase-I binding loop and the Phe 223 to Ala 230 helix has been demonstrated by our limited digestion experiments showing an exposure of proteolytic cleavage sites within segment 227-235 in ECP-modified F-actin.…”

Section: Discussionmentioning

confidence: 99%

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The DNase-I Binding Loop of Actin May Play a Role in the Regulation of Actin-Myosin Interaction by Tropomyosin/Troponin

Moraczewska

Gruszczynska-Biegala

Redowicz

et al. 2004

Journal of Biological Chemistry

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, on its interaction with myosin S1 in the presence and absence of tropomyosin or tropomyosin-troponin. Both individual modifications reduced activation of S1 ATPase by actin to a similar extent. The effect of ECP cleavage, but not of subtilisin cleavage, was partially reversed by stabilization of interprotomer contacts with phalloidin, indicating different pathways of signal transmission from the N-and C-terminal parts of loop 38 -52 to myosin binding sites. ECP cleavage diminished the affinity to tropomyosin and reduced its inhibition of acto-S1 ATPase at low S1 concentrations, but increased the tropomyosin-mediated cooperative enhancement of the ATPase by S1 binding to actin. These effects were reversed by phalloidin. Subtilisin-cleaved actin more closely resembled unmodified actin than the ECP-modified actin. Limited proteolysis of the modified and unmodified F-actins revealed an allosteric effect of ECP cleavage on the conformation of the actin subdomain 4 region that is presumably involved in tropomyosin binding. Our results point to a possible role of the N-terminal part of loop 38 -52 of actin in communication between tropomyosin and myosin through changes in actin structure.

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Section: Discussionsupporting

confidence: 80%

Section: Discussionmentioning

confidence: 99%

The DNase-I Binding Loop of Actin May Play a Role in the Regulation of Actin-Myosin Interaction by Tropomyosin/Troponin

Moraczewska

Gruszczynska-Biegala

Redowicz

et al. 2004

Journal of Biological Chemistry

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“…Numerous cross-linking experiments provide supporting evidence for residues expected to be proximal based on models of F-actin. Cross-linking data are available both for protomers related in the lateral direction [i.e., sideways between the two helical strands (18)(19)(20)] and for protomers related in the longitudinal direction [i.e., along one vertical strand of the two stranded F-actin helix (19,21)]. Data from synchrotron x-ray radiolysis experiments, probing the reactivity of solvent-accessible residues, are also consistent with structural models (22).…”

mentioning

confidence: 54%

“…Longitudinal dimers are of particular interest for structure determination because many actin-binding proteins attach to two longitudinally adjacent protomers in F-actin. Some information is already available regarding the approximate regions of contact between molecules at this interface (18)(19)(20)(21). A more detailed view of the interface would effectively define the strand structure in F-actin and also could constrain models of the complete double-stranded filament.…”

Section: Results and Analysismentioning

confidence: 99%

The crystal structure of a cross-linked actin dimer suggests a detailed molecular interface in F-actin

Kudryashov

Sawaya

Adisetiyo

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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The 2.5-Å resolution crystal structure is reported for an actin dimer, composed of two protomers cross-linked along the longitudinal (or vertical) direction of the F-actin filament. The crystal structure provides an atomic resolution view of a molecular interface between actin protomers, which we argue represents a near-native interaction in the F-actin filament. The interaction involves subdomains 3 and 4 from distinct protomers. The atomic positions in the interface visualized differ by 5-10 Å from those suggested by previous models of F-actin. Such differences fall within the range of uncertainties allowed by the fiber diffraction and electron microscopy methods on which previous models have been based. In the crystal, the translational arrangement of protomers lacks the slow twist found in native filaments. A plausible model of F-actin can be constructed by reintroducing the known filament twist, without disturbing significantly the interface observed in the actin dimer crystal.actin crystal structure ͉ F-actin filament ͉ motor proteins A ctin is one of the most highly conserved proteins in nature, where it plays key roles in contraction, cell shape and motility, and subcellular organization. Actin's myriad functions are regulated by protein-protein interactions. Besides interacting with an enormously diverse set of other cellular proteins (1), actin's most critical functions arise from its interactions with itself as it assembles to form F-actin filaments. Because actin carries out its cellular functions through its filamentous form, knowing the detailed structure of actin filaments is an important step in achieving a mechanistic understanding of actin function.Our understanding of actin has been advanced greatly by intensive investigation into its three-dimensional (3D) structure. Because the filamentous form of actin is essentially incompatible with the growth of 3D crystals, crystallographic studies have focused on actin in its monomeric form. The 3D structure of monomeric actin (G-actin) was determined first by Kabsch et al.(2) as a complex, with DNase I serving as a polymerization inhibitor. The crystal structure of monomeric actin has since been determined at atomic resolution under a variety of conditions, varying, for example, in actin isoform (3), the identity of the bound nucleotide (4, 5), and in the identity of the other proteins (6, 7) or small molecules added as polymerization inhibitors (8, 9). As a consequence, the structure of the actin monomer (G-actin) is understood in considerable detail, although some important issues remain open regarding nucleotide-dependent changes in G-actin structure, including a possible transition between the open and closed nucleotide cleft conformations and the order-disorder shift of the DNase I-binding loop (4,7,10).Structural models of the actin filament have derived mainly from methods other than crystallography. The first structural model of F-actin was obtained by Holmes et al. (11), by using fiber-diffraction data extending to 8.4-Å resolution to determi...

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“…Polymerization time was either 2 min or 2 h at room temperature. Wild-type yeast actin was prepared as described (14), and G-actin was polymerized in 50 mM NaCl͞3 mM MgCl 2 ͞10 mM 4-morpholinepropanesulfonic acid (Mops), pH 7.6͞0.5 mM ATP for 2 h. Tetramethylrhodamine (TMR)-labeled actin was prepared as described (15). A mixture of 10 M G-TMR-actin͞10 M unlabeled G-actin͞10 mM Hepes, pH 7.5͞0.5 mM ATP was converted to Mg 2ϩ form by incubation with EGTA and MgCl 2 and then polymerized by 50 mM KCl͞2 mM MgCl 2 over 3 h. F-Mg 2ϩ -TMR copolymers were diluted to 1.5 M before application to EM grids.…”

Section: Methodsmentioning

confidence: 99%

Actin-destabilizing factors disrupt filaments by means of a time reversal of polymerization

Orlova

Shvetsov

Galkin

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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Actin, one of the most highly conserved and abundant eukaryotic proteins, is constantly being polymerized and depolymerized within cells as part of cellular motility, tissue formation and repair, and embryonic development. Many proteins exist that bind to monomeric or filamentous (F) forms of actin to regulate the polymerization state. It has become increasingly apparent that the ability of different proteins to bind to and regulate actin filament dynamics depends on the ability of the filament to exist in altered conformations. Yet, little is known about how these conformational changes occur at the molecular level. We have destabilized F-actin filaments by forming a disulfide that locks the ''hydrophobic plug'' to the body of the actin subunit or by altering the C terminus of actin with a tetramethylrhodamine label. We also examined F-actin filaments at short times after the initiation of polymerization. In all three cases, a substantial fraction of protomers can be found in a ''tilted'' state that also is induced by actin depolymerizing factor͞cofilin proteins. These observations suggest that F-actin filaments are annealed over time into a stable filament and that actin-depolymerizing proteins can effect a time reversal of polymerization.cytoskeleton ͉ EM ͉ image analysis

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Cross-linking constraints on F-actin structure 1 1Edited by M. F. Moody

Cited by 61 publications

References 36 publications

The DNase-I Binding Loop of Actin May Play a Role in the Regulation of Actin-Myosin Interaction by Tropomyosin/Troponin

The DNase-I Binding Loop of Actin May Play a Role in the Regulation of Actin-Myosin Interaction by Tropomyosin/Troponin

The crystal structure of a cross-linked actin dimer suggests a detailed molecular interface in F-actin

Actin-destabilizing factors disrupt filaments by means of a time reversal of polymerization

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