Activation of the Adenosine Triphosphatase of <i>Limulus polyphemus</i> Actomyosin by Tropomyosin

Lehman, William; Szent‐Györgyi, Albert

doi:10.1085/jgp.59.4.375

Cited by 55 publications

(6 citation statements)

References 25 publications

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“…However, the same studies indicated that the strongly bound myosin also ''potentiated'' actin-activated myosin ATPase to higher-than-control values, but only when tropomyosin was present in the assays performed, and not when actin was free of tropomyosin. These results mimicked observations previously noted for some invertebrate preparations (28). Hence, the suggestion of a discrete, tropomyosin-dependent ''potentiated state'' of the thin filament emerged.…”

Section: Close Encounters With Early Literaturesupporting

confidence: 88%

Switching Muscles On and Off in Steps: The McKillop-Geeves Three-State Model of Muscle Regulation

Lehman

2017

Biophysical Journal

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Section: Close Encounters With Early Literaturesupporting

confidence: 88%

Switching Muscles On and Off in Steps: The McKillop-Geeves Three-State Model of Muscle Regulation

Lehman

2017

Biophysical Journal

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“…Phosphorylation of the 20 000-dalton light chain is essential for this effect to occur. Potentiation of actin-activated ATPase activity by tropomyosin has also been reported for rabbit skeletal muscle under conditions that favor rigor complexes (Bremel et al, 1972) and in Limulus striated myosin at high ATP concentrations where the rigor complexes were minimal (Lehman & Szent-Gyorgyi, 1972). A recent report by Sellers (1980) indicates that the actin-activated ATPase activity in Limulus myosin is dependent on myosin light-chain phosphorylation.…”

Section: Discussionmentioning

confidence: 76%

Effects of phosphorylation, calcium ion, and tropomyosin on actin-activated adenosine 5'-triphosphatase activity of mammalian smooth muscle myosin

Chacko¹

1981

Biochemistry

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Actomyosin isolated from bovine stomach muscle contains the endogenous light-chain kinase and phosphatase. Myosin can be separated from other proteins by gel filtration on a Sepharose 4B--agarose column. The amount of phosphate covalently bound to the 20 000-dalton light chains of purified myosin can be controlled by phosphorylation or dephosphorylation using the endogenous enzymes prior to column purification. The purified myosin can serve as a substrate for exogenously added light-chain kinase and phosphatase, but the myosin itself is free of the activities for both enzymes. The adenosine 5'-triphosphatase (ATPase) activity of myosin was activated by rabbit skeletal muscle actin only when the 20 000-dalton light chain was phosphorylated. The level of activation correlated with the amount of phosphate bound to the light chain. The maximum activation by pure actin was observed when the molar ratio of myosin to actin was 1:20. The activation was dependent on the amount of phosphate bound to the myosin light chain at all levels of actin concentrations. The actin-activated ATPase activity of stomach muscle myosin is not dependent on Ca2+ concentration once the myosin is phosphorylated and is free of kinase and phosphatase activity. The actin-activated ATPase activity was higher when the actin was complexed with tropomyosin. The highest level of activation was obtained when the myosin was fully phosphorylated and the actin was complexed with tropomyosin at a molar ratio of 1:6 (Tm/A). The potentiation of actin-activated ATP hydrolysis by tropomyosin is not dependent on Ca2+. These data indicate that tropomyosin plays a major role in the actin-activated ATP hydrolysis by smooth muscle myosin in the absence of other regulatory proteins.

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“…Fractions of 3 ml were collected and analyzed by SDS PAGE (21). Those fractions showing the tropomyosin A and B chains, and containing no higher molecularweight contaminants, were pooled and dialyzed against 5 mM Tris-HCl and 50 mM MgCl2, pH 8.0 (23).…”

Section: Methodsmentioning

confidence: 99%

Cytoskeletal components of the vertebrate neuromuscular junction: vinculin, alpha-actinin, and filamin.

Bloch¹,

Hall²

1983

The Journal of Cell Biology

150

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We have used immunocytochemical methods to investigate the cytoskeletal constituents of the vertebrate neuromuscular junction. Specific, affinity-purified antibodies to three cytoskeletal proteins, vinculin, a-actinin, and filamin, bound to neuromuscular junctions in sections of normal rat, mouse, chick, and Xenopus muscles. All three antibodies bound to the synaptic regions of denervated rat muscle fibers, indicating that the proteins recognized by these antibodies are associated with postsynaptic structures. The three proteins are present at the neuromuscular junction in muscle fibers of embryonic and neonatal animals, and therefore, may play an important role in its differentiation.The postsynaptic membrane of the adult vertebrate neuromuscular junction has a highly specialized structure that is distinct from the extrasynaptic membrane that surrounds it. Within its borders, the postsynaptic membrane is organized into distinct domains that are either rich or poor in acetylcholine receptors (AChR). The AChR-rich domains, which contain paracrystalline arrays of AChR (16,27, 30), are closely apposed to the nerve terminals (10), whereas the AChR-poor domains are invaginated to form more or less elaborate folds according to the species and the muscle type (41).Although the factors responsible for the differentiation of the postsynaptic membrane and its organization into AChRrich and AChR-poor domains are not yet understood, the structures in close association with the membrane on each of its surfaces may play important roles. The postsynaptic membrane is bounded extraceilularly by a basal lamina that has unique structural and functional properties (17, 3 I) and that, in adult muscle, can direct the differentiation of both presynaptic and postsynaptic membranes (1,7,25,31,32). The postsynaptic membrane is associated intracellularly with a layer of electron-dense material that is coextensive with the AChR-rich domain and with an extensive network of cytoskeletal filaments (16-18, 29, 30). The involvement in other cells of cytoskeletal elements in generating and maintaining membrane protein aggregates and specialized configurations of the membrane suggest that these may also be important in determining the structure of the postsynaptic membrane at the neuromuscular junction. Two proteins, one that resembles actin (15) and another that is immunologically related to the 43,000-dalton protein in Torpedo (12, 33, 34), have been THE JOURNAL OF CELL BIOLOGY • VOLUME 97 JULY 1983 217-223 © The Rockefeller University Press . 0021-9525/83/07/0217/07 $1.00 associated with postsynaptic structures at the neuromuscular junction. Here we report that proteins related to vinculin, aactinin, and filamin are also concentrated postsynaptically. MATERIALS AND METHODS Staining of Frozen Sections::Frozen muscle sections were cut as described previously (15,31). Briefly, muscles were dissected and frozen in liquid nitrogen or in hexane precooled in a dry ice-acetone hath. Muscles from embryonic and newborn rats were wrapped in a st...

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Activation of the Adenosine Triphosphatase of Limulus polyphemus Actomyosin by Tropomyosin

Cited by 55 publications

References 25 publications

Switching Muscles On and Off in Steps: The McKillop-Geeves Three-State Model of Muscle Regulation

Switching Muscles On and Off in Steps: The McKillop-Geeves Three-State Model of Muscle Regulation

Effects of phosphorylation, calcium ion, and tropomyosin on actin-activated adenosine 5'-triphosphatase activity of mammalian smooth muscle myosin

Cytoskeletal components of the vertebrate neuromuscular junction: vinculin, alpha-actinin, and filamin.

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