UNC45B is a multidomain molecular chaperone that is essential for the proper folding and function of myosin. It has previously been demonstrated that the UCS domain is responsible for the chaperoning function of UNC45B and that removing its client-binding loop leads to a significant change in its solution conformation and a reduced chaperoning function. Here, we report the direct quantification of affinities of myosin binding to wild type and mutant UNC45B using surface plasmon resonance (SPR) spectroscopy. We found that deletion of the client-binding loop in UNC45B resulted in a dramatic decrease in myosin affinity.
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http://dx.doi.org/10.17912/micropub.biology.001131 | DOI Listing |
ESC Heart Fail
January 2025
Department of Cardiology, Stavanger University Hospital, Stavanger, Norway.
Background: Cardiac myosin binding protein C (cMyC) is an emerging new biomarker of myocardial injury rising earlier and cleared faster than cardiac troponins. It has discriminatory power similar to high-sensitive troponins in diagnosing myocardial infarction in patients presenting with chest pain. It is also associated with outcome in patients with acute heart failure.
View Article and Find Full Text PDFNat Commun
January 2025
Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA.
Assembly of actin-based stereocilia is critical for cochlear hair cells to detect sound. To tune their mechanosensivity, stereocilia form bundles composed of graded rows of ascending height, necessitating the precise control of actin polymerization. Myosin 15 (MYO15A) drives hair bundle development by delivering critical proteins to growing stereocilia that regulate actin polymerization via an unknown mechanism.
View Article and Find Full Text PDFJ Physiol Sci
January 2025
Department of Frontier Health Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, 7-2-10 Higashiogu, Arakawa-Ku, 116-8551, Tokyo, Japan. Electronic address:
Actin linked regulatory mechanisms are known to contribute contraction/relaxation in smooth muscle. In order to clarify whether modulation of polymerization/depolymerization of actin filaments affects relaxation process, we examined the effects of cytochalasin D on relaxation process by Ca removal after Ca-induced contraction of β-escin skinned (cell membrane permeabilized) taenia cecum and carotid artery preparations from guinea pigs. Cytochalasin D, an inhibitor of actin polymerization, significantly suppressed the force during relaxation both in skinned taenia cecum and carotid artery.
View Article and Find Full Text PDFFront Physiol
January 2025
Institute of Vegetative Physiology, University of Cologne, Köln, Germany.
Objective: Previous studies on muscle fibers, myofibrils, and myosin revealed that the release of inorganic phosphate (P) and the force-generating step(s) are reversible, with cross-bridges also cycling backward through these steps by reversing force-generating steps and rebinding P. The aim was to explore the significance of force redevelopment kinetics (rate constant ) in cardiac myofibrils for the coupling between the P binding induced force reversal and the rate-limiting transition for backward cycling of cross-bridges from force-generating to non-force-generating states.
Methods: and force generation of cardiac myofibrils from guinea pigs were investigated at 0.
Biophys Rev
December 2024
Randall Centre for Cell & Molecular Biophysics, New Hunt's House, Guy's Campus, King's College London, London, UK.
Calcium binding to troponin triggers the contraction of skeletal and heart muscle through structural changes in the thin filaments that allow myosin motors from the thick filaments to bind to actin and drive filament sliding. Here, we review studies in which those changes were determined in demembranated fibres of skeletal and heart muscle using fluorescence for in situ structure (FISS), which determines domain orientations using polarised fluorescence from bifunctional rhodamine attached to cysteine pairs in the target domain. We describe the changes in the orientations of the N-terminal lobe of troponin C (TnC) and the troponin IT arm in skeletal and cardiac muscle cells associated with contraction and compare the orientations with those determined in isolated cardiac thin filaments by cryo-electron microscopy.
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