Papers by Joseph Chalovich
Frontiers in physics, Jan 25, 2024
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Biophysical Journal, Feb 1, 2022
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Proceedings of the National Academy of Sciences of the United States of America, Aug 1, 1983
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Biochemistry, Jun 28, 2023
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Biophysical Journal, 2015
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Frontiers in Physiology, Mar 24, 2020
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Biochemistry, Oct 19, 2020
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Biophysical Journal, 2014
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Biology of Reproduction, Jul 1, 1993
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Biophysical Journal, Aug 1, 2018
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Journal of Biological Chemistry, Apr 1, 1987
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Journal of Biological Chemistry, Feb 1, 1990
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Frontiers in Physiology, Mar 28, 2023
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Cambridge University Press eBooks, Aug 28, 1997
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Biochemistry, May 1, 2003
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Biochemistry, Aug 25, 2020
Calcium binding to troponin C (TnC) is insufficient for full activation of myosin ATPase activity... more Calcium binding to troponin C (TnC) is insufficient for full activation of myosin ATPase activity by actin-tropomyosin-troponin. Previous attempts to investigate full activation utilized ATP-free myosin or chemically modified myosin to stabilize the active state of regulated actin. We utilized the Δ14-TnT and the A8V-TnC mutants to stabilize the activated state at saturating Ca2+ and to eliminate one of the inactive states at low Ca2+. The observed effects differed in solution studies and in the more ordered in vitro motility assay and in skinned cardiac muscle preparations. At saturating Ca2+, full activation with Δ14-TnT·A8V-TnC decreased the apparent KM for actin-activated ATPase activity compared to bare actin filaments. Rates of in vitro motility increased at both high and low Ca2+ with Δ14-TnT; the maximum shortening speed at high Ca2+ increased 1.8-fold. Cardiac muscle preparations exhibited increased Ca2+ sensitivity and large increases in resting force with either Δ14-TnT or Δ14-TnT·A8V-TnC. We also observed a significant increase in the maximal rate of tension redevelopment. The results of full activation with Ca2+ and Δ14-TnT·A8V-TnC confirmed and extended several earlier observations using other means of reaching full activation. Furthermore, at low Ca2+, elimination of the first inactive state led to partial activation. This work also confirms, in three distinct experimental systems, that troponin is able to stabilize the active state of actin-tropomyosin-troponin without the need for high-affinity myosin binding. The results are relevant to the reason for two inactive states and for the role of force producing myosin in regulation.
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Biochemistry, May 6, 2022
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Biophysical Journal, Mar 1, 2002
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Archives of Biochemistry and Biophysics, Feb 1, 1980
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Journal of Muscle Research and Cell Motility, Sep 23, 2005
Fesselin is an actin binding protein that bundles actin filaments and accelerates nucleation of a... more Fesselin is an actin binding protein that bundles actin filaments and accelerates nucleation of actin polymerization. The effect of fesselin on actin polymerization is regulated by Ca(++)-calmodulin. Because actin filaments serve both structural and contractile functions we also examined the effect of fesselin on activation of myosin S1 ATPase activity. Fesselin inhibited the activation of S1-catalyzed ATP hydrolysis in a similar manner in both the presence and absence of tropomyosin. This inhibition was unaffected by Ca(++)-calmodulin. Fesselin inhibited the binding of myosin-S1 to actin during steady-state ATP hydrolysis. Fesselin also displaced caldesmon from actin. S1 displaced fesselin from actin in the absence of nucleotide when the affinity of S1 for actin was much greater than the affinity of fesselin for actin. It is likely that fesselin and S1 share common binding sites on F-actin. We also observed that fesselin could bind to smooth muscle myosin with muM affinity. Fesselin shares some similarities to caldesmon in binding to several other proteins and having multiple potential functions.
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Papers by Joseph Chalovich