Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q9Y573 (actin-binding protein)
 1,734 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A highly branched filament network is the principal structure in the periphery of detergent-extracted cytoskeletons of macrophages that have been spread on a surface and either freeze or critical point dried, and then rotary shadowed with platinum-carbon. This array of filaments completely fills lamellae extended from the cell and bifurcates to form 0.2-0.5 micron thick layers on the top and bottom of the cell body. Reaction of the macrophage cytoskeletons with anti-actin IgG and with anti-IgG bound to colloidal gold produces dense staining of these filaments, and incubation with myosin subfragment 1 uniformly decorates these filaments, identifying them as actin. 45% of the total cellular actin and approximately 70% of actin-binding protein remains in the detergent-insoluble cell residue. The soluble actin is not filamentous as determined by sedimentation analysis, the DNAase I inhibition assay, and electron microscopy, indicating that the cytoskeleton is not fragmented by detergent extraction. The spacing between the ramifications of the actin network is 94 +/- 47 nm and 118 +/- 72 nm in cytoskeletons prepared for electron microscopy by freeze drying and critical point drying, respectively. Free filament ends are rare, except for a few which project upward from the body of the network or which extend down to the substrate. Filaments of the network intersect predominantly at right angles to form either T-shaped and X-shaped overlaps having striking perpendicularity or else Y-shaped intersections composed of filaments intersecting at 120-130 degrees angles. The actin filament concentration in the lamellae is high, with an average value of 12.5 mg/ml. The concentration was much more uniform in freeze-dried preparations than in critical point-dried specimens, indicating that there is less collapse associated with the freezing technique. The orthogonal actin network of the macrophage cortical cytoplasm resembles actin gels made with actin-binding protein. Reaction of cell cytoskeletons and of an actin gel made with actin-binding protein with anti-actin-binding protein IgG and anti-IgG-coated gold beads resulted in the deposition of clusters of gold at points where filaments intersect and at the ends of filaments that may have been in contact with the membrane before its removal with detergent. In the actin gel made with actin-binding protein, 75% of actin-fiber intersections labeled, and the filament spacing between intersections is consistent with that predicted on theoretical grounds if each added actin-binding protein molecule cross-links two filaments to form an intersection in the gel.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The architecture of actin filaments and the ultrastructural location of actin-binding protein in the periphery of lung macrophages. 374 63

The retinal pigmented epithelium (RPE) is a simple cuboidal epithelium with apical processes which, unlike many epithelia, do not extend freely into a lumen but rather interdigitate closely with the outer segments of the neural retina. To determine whether this close association was reflected in the cytoskeletal organization of the RPE, we studied the components of the cytoskeleton of the RPE and their localization in the body of the cell and in the apical processes. By relative mobility on SDS gels and by immunoblotting, we identified actin, vimentin, myosin, spectrin (240/235), and alpha-actinin as major components, and vinculin as a minor component. In addition, the RPE cytoskeleton contains polypeptides of Mr 280,000 and 250,000; the latter co-electrophoreses with actin-binding protein. By immunofluorescence, the terminal web region appeared similar to the comparable region of the intestinal epithelium that consists of broad belts of microfilaments containing myosin, actin, spectrin, and alpha-actinin. However, the components of the apical processes were very different from those of intestinal microvilli. We observed staining along the process for myosin, actin, spectrin, alpha-actinin, and vinculin. The presence in the apical processes of contractile proteins and also of proteins typically found at sites of cell attachments suggests that the RPE may actively adhere to, and exert tension on, the neural retina.
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PMID:Components of the cytoskeleton in the retinal pigmented epithelium of the chick. 392 78

The platelet cytoskeleton is a major determinant of platelet morphology and function. Changes in the protein composition of the cytoskeleton were studied during storage of platelets at 20 degrees to 24 degrees C under blood banking conditions. Cytoskeletons were prepared by extraction of washed platelets with the detergent Triton X-100 and then analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In addition to the three major proteins visible with Coomassie blue staining--actin, myosin, and actin-binding protein--silver staining revealed other proteins associated with the cytoskeletons of freshly collected and stored platelets. The resting platelet cytoskeleton contained 8% to 10% of the total platelet protein and approximately 50% of the total actin. During storage of platelet concentrates for up to five days in the PL 732 container, proteins of 50,000 to 55,000 and 90,000 mol wt were increasingly incorporated into the Triton-insoluble fraction, whereas the amounts of cytoskeleton-associated actin-binding protein, myosin, and actin were maintained at levels present in fresh platelets. Storage of platelets under conditions that allowed the reduction of platelet concentration pH to nearly 6.0 resulted in a marked decrease in the amounts of the major proteins of the cytoskeleton. The loss of specific proteins from platelets stored for extended periods with reduced pH, accompanied by the appearance of lower molecular weight proteins in the cytoskeleton, suggests that extensive proteolysis may occur under certain storage conditions. These data show that the conditions employed for storage of platelet concentrates influence the protein composition of the cytoskeleton and the total protein content of the platelet.
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PMID:Effects of storage conditions on platelet cytoskeletal proteins. 398 48

The effects of lysoPC, four other amphiphiles containing a linear 16 carbon alkane tail and chlorpromazine on platelet cytoskeletal assembly were compared. LysoPC and nonmetabolized amphiphiles all caused time-dependent inhibition followed by potentiation of thrombin-induced aggregation, serotonin secretion and cytoskeletal assembly in gel-filtered platelets, a result which ruled out hydrolysis of the amphiphiles as the mechanism of the time dependence. Hexadecanesulfonate was superior as a potentiator and cetyltrimethyl ammonium bromide (CTAB) was a better inhibitor. On the contrary, inhibition of platelet activation by arachidonate was not effected in a time-dependent manner and the actin-crosslinking proteins, actin-binding protein and myosin, were selectively prevented from incorporation into cytoskeletal cores, although protein phosphorylation and actin polymerization still occurred. Chlorpromazine also showed this selective inhibition of cytoskeletal assembly. LysoPC at concentrations which have been reported to cause development of filopodia did increase slightly the amount of actin present in Triton X-100-insoluble cores but not protein phosphorylation or incorporation of actin-crosslinking proteins. The effective concentrations of lysoPC and chlorpromazine can be predicted from the Meyer-Overton-Mullins rule of anesthesia which indicates their general effectiveness, but their specific effects only partially overlap.
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PMID:The effects of lysophosphatidylcholine and related amphiphiles on platelet cytoskeletal assembly. 609 54

Actomyosin Mg2+-ATPase activity was stimulated by a brain microtubule-associated protein (MAP) fraction. The stimulating activity of the MAP fraction was abolished by boiling and trypsin treatment, suggesting the presence of a protein factor. The factor stimulated actomyosin Mg2+-ATPase activity stoichiometrically by about four times in the optimum conditions (50--75 mM KCl, pH 6.6). The stimulating factor was coprecipitable with actomyosin and was found to be a pair of high-molecular-weight polypeptides (mol wts, 240,000 and 235,000). The polypeptides were not associated with microtubules or myosin, but with fibrous actin. In column chromatographies used for purifying the stimulating factor, the amount of polypeptides coincided with the stimulating activity. Increases in both specific activity and the amount of the paired polypeptides were nearly parallel in the process of the purification. A purified fraction (65% pure with respect to the paired polypeptides) showed a 56-fold increase of the specific stimulating activity as compared with the initial brain supernatant. The two peptides were similar but not identical with filamin and spectrin in terms of electrophoretic mobility. Hence, the pair of polypeptides was identified as an actin-binding protein newly found in brain.
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PMID:Stimulation of actomyosin Mg2+-ATPase activity by a brain microtubule-associated protein fraction. High-molecular-weight actin-binding protein is the stimulating factor. 612 91

In the plasmodia of Physarum polycephalum, which show a cyclic contraction-relaxation rhythm of the gel layer, huge aggregates of entangled actin microfilaments are formed at about the onset of the relaxation (R. Nagai, Y. Yoshimoto, and N. Kamiya. 1978. J. Cell Sci. 33:205-225). By treating the plasmodia with Triton X-100, we prepared a demembranated cytoskeleton consisting of entangled actin filaments and found that the actin filaments hardly interact with rabbit skeletal myosin. From the cytoskeleton we purified a novel actin-binding protein which binds stoichiometrically to actin and makes actin filaments curled and aggregated. It also inhibits the ATPase activity as well as the superprecipitation of reconstituted rabbit skeletal muscle actomyosin. This protein has a polypeptide molecular weight of 36,000 and binds 7 mol of actin/mol 36,000 polypeptide.
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PMID:A novel 36,000-dalton actin-binding protein purified from microfilaments in Physarum plasmodia which aggregates actin filaments and blocks actin-myosin interaction. 612 81

The intestinal epithelium provides an excellent starting material for the isolation of natural microfilament organizations in amounts suitable for biochemical studies. The microvillus filament bundle core and the terminal web provide two distinct microfilament systems. We review the current knowledge of the filament bundle core and the attempts that have been made to reconstitute this structure from actin and its four major associated proteins. We show in addition that a high molecular mass actin-binding protein (TW-260/240) having spectrin-like properties is, next to myosin, the major associated protein of the terminal web retained in isolated brush borders. We summarize the biochemical and morphological evidence for the existence of a class of spectrin-related molecules in the cortical cytoplasm of many cell types. These findings may lead to a new understanding of membrane-microfilament interactions.
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PMID:Microfilament-membrane interaction: the brush border of intestinal epithelial cells as a model. 612 57

We found that a small, reproducible amount of calmodulin is present in the cytoskeleton of human platelets. Triton-insoluble materials (cytoskeletons), which were prepared by centrifugation at 1000 X g for 10 min of platelets after lysis by Triton X-100, stimulated cyclic AMP phosphodiesterase activity in the presence of Ca2+ but not in the presence of the calcium chelator, EGTA, or the calmodulin antagonist, trifluoperazine. The activation of the enzyme was also obtained after heating Triton-insoluble materials. An alkaline glycerol polyacrylamide gel electrophoresis of fractions obtained after gel filtration of solubilized Triton residues showed a protein band which had a faster electrophoretic mobility in the absence than in the presence of Ca2+. Upon thrombin activation of platelets, calmodulin in the Triton-insoluble cytoskeletons increased rapidly parallel to actin, actin-binding protein and myosin. With other stimulants such as collagen, epinephrine and ADP, similar results were obtained but with slower association of these proteins with cytoskeletons. However, after treatment with the Ca2+-ionophore A23187, calmodulin, actin and actin-binding protein in Triton residues decreased rapidly, whereas the association of myosin increased. Thus, calmodulin seems to be associated with actin filaments rather than myosin filaments, and may be involved in the generation of contractile force in the cell.
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PMID:Presence of calmodulin in human platelet cytoskeletons and its concentration change upon activation of platelets. 614 9

Caldesmon, a major calmodulin- and actin-binding protein of smooth muscle (Sobue, K., Muramoto, Y., Fujita, M., and Kakiuchi, S. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 5652-5655), has been obtained in highly purified form from chicken gizzard by a modification of a previously published procedure (Ngai, P. K., Carruthers, C. A., and Walsh, M. P. (1984) Biochem. J. 218, 863-870) and was found to cause a significant inhibition of both superprecipitation and actin-activated myosin Mg2+-ATPase activity in a system reconstituted from the purified contractile and regulatory proteins without influencing the phosphorylation state of myosin. This inhibitory effect was seen both in the presence and absence of tropomyosin. A Ca2+-and calmodulin-dependent kinase which catalyzed phosphorylation of caldesmon was identified in chicken gizzard; this kinase is distinct from myosin light-chain kinase. Caldesmon prepared by calmodulin-Sepharose affinity chromatography was contaminated with caldesmon kinase activity and was unable to inhibit actomyosin ATPase activity or superprecipitation. Phosphatase activity capable of dephosphorylating caldesmon was also identified in smooth muscle. These results indicate that caldesmon can inhibit smooth muscle actomyosin ATPase activity in vitro, and this function may itself be subject to regulation by reversible phosphorylation of caldesmon.
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PMID:Inhibition of smooth muscle actin-activated myosin Mg2+-ATPase activity by caldesmon. 615 36

Measurements of total proteins, myosin, actin, actin-binding protein, and ATPase activity of myosin were examined in platelets from patients with idiopathic scoliosis and from healthy individuals. Abnormalities in the distribution of total and contractile proteins were revealed after fractionations. The insoluble fraction of the patients' platelets had a higher, and the cytosol fraction had a lower than normal protein content. Similar differences were observed in the specific activity of myosin ATPase. These findings show that in patients with idiopathic scoliosis platelet defects exist and that their study might be useful in research of the disease.
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PMID:Contractile protein studies on platelets from patients with idiopathic scoliosis. 621


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