Converter domain mutations in myosin alter structural kinetics and motor function.

Autor:	Gunther LK; Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033., Rohde JA; Department of Biochemistry, Biophysics and Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455., Tang W; Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033., Walton SD; Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033., Unrath WC; Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033., Trivedi DV; Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033., Muretta JM; Department of Biochemistry, Biophysics and Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455., Thomas DD; Department of Biochemistry, Biophysics and Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455., Yengo CM; Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033. Electronic address: cmy11@psu.edu.
Jazyk:	angličtina
Zdroj:	The Journal of biological chemistry [J Biol Chem] 2019 Feb 01; Vol. 294 (5), pp. 1554-1567. Date of Electronic Publication: 2018 Dec 05.
DOI:	10.1074/jbc.RA118.006128
Abstrakt:	Myosins are molecular motors that use a conserved ATPase cycle to generate force. We investigated two mutations in the converter domain of myosin V (R712G and F750L) to examine how altering specific structural transitions in the motor ATPase cycle can impair myosin mechanochemistry. The corresponding mutations in the human β-cardiac myosin gene are associated with hypertrophic and dilated cardiomyopathy, respectively. Despite similar steady-state actin-activated ATPase and unloaded in vitro motility-sliding velocities, both R712G and F750L were less able to overcome frictional loads measured in the loaded motility assay. Transient kinetic analysis and stopped-flow FRET demonstrated that the R712G mutation slowed the maximum ATP hydrolysis and recovery-stroke rate constants, whereas the F750L mutation enhanced these steps. In both mutants, the fast and slow power-stroke as well as actin-activated phosphate release rate constants were not significantly different from WT. Time-resolved FRET experiments revealed that R712G and F750L populate the pre- and post-power-stroke states with similar FRET distance and distance distribution profiles. The R712G mutant increased the mole fraction in the post-power-stroke conformation in the strong actin-binding states, whereas the F750L decreased this population in the actomyosin ADP state. We conclude that mutations in key allosteric pathways can shift the equilibrium and/or alter the activation energy associated with key structural transitions without altering the overall conformation of the pre- and post-power-stroke states. Thus, therapies designed to alter the transition between structural states may be able to rescue the impaired motor function induced by disease mutations. (© 2019 Gunther et al.)
Databáze:	MEDLINE
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