Molecular regulatory mechanism of human myosin-7a.

Autor:	Holló A; Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA; Department of Biophysics, University of Pécs Medical School, Pécs, Hungary., Billington N; Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA; Department of Biochemistry & Molecular Medicine, School of Medicine, West Virginia University, Morgantown, West Virginia, USA; Microscope Imaging Facility, West Virginia University, Morgantown, West Virginia, USA., Takagi Y; Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA., Kengyel A; Department of Biophysics, University of Pécs Medical School, Pécs, Hungary; Institute for Biophysical Chemistry, Hannover Medical School, Hannover, Germany., Sellers JR; Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA. Electronic address: sellersj@nhlbi.nih.gov., Liu R; Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA; Department of Biochemistry & Molecular Medicine, School of Medicine, West Virginia University, Morgantown, West Virginia, USA. Electronic address: rong.liu@hsc.wvu.edu.
Jazyk:	angličtina
Zdroj:	The Journal of biological chemistry [J Biol Chem] 2023 Oct; Vol. 299 (10), pp. 105243. Date of Electronic Publication: 2023 Sep 09.
DOI:	10.1016/j.jbc.2023.105243
Abstrakt:	Myosin-7a is an actin-based motor protein essential for vision and hearing. Mutations of myosin-7a cause type 1 Usher syndrome, the most common and severe form of deafblindness in humans. The molecular mechanisms that govern its mechanochemistry remain poorly understood, primarily because of the difficulty of purifying stable intact protein. Here, we recombinantly produce the complete human myosin-7a holoenzyme in insect cells and characterize its biochemical and motile properties. Unlike the Drosophila ortholog that primarily associates with calmodulin (CaM), we found that human myosin-7a utilizes a unique combination of light chains including regulatory light chain, CaM, and CaM-like protein 4. Our results further reveal that CaM-like protein 4 does not function as a Ca 2+ sensor but plays a crucial role in maintaining the lever arm's structural-functional integrity. Using our recombinant protein system, we purified two myosin-7a splicing isoforms that have been shown to be differentially expressed along the cochlear tonotopic axis. We show that they possess distinct mechanoenzymatic properties despite differing by only 11 amino acids at their N termini. Using single-molecule in vitro motility assays, we demonstrate that human myosin-7a exists as an autoinhibited monomer and can move processively along actin when artificially dimerized or bound to cargo adaptor proteins. These results suggest that myosin-7a can serve multiple roles in sensory systems such as acting as a transporter or an anchor/force sensor. Furthermore, our research highlights that human myosin-7a has evolved unique regulatory elements that enable precise tuning of its mechanical properties suitable for mammalian auditory functions. Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article. (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)
Databáze:	MEDLINE
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