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J Biol Chem. 2018 Jun 8;293(23):9017-9029. doi: 10.1074/jbc.RA118.001938. Epub 2018 Apr 17.

Dilated cardiomyopathy myosin mutants have reduced force-generating capacity.

Author information

1
From the School of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom.
2
the Department of Biophysics, University of Pécs, Medical School, Szigeti Street 12, H-7624 Pécs, Hungary.
3
the BioFrontiers Institute and Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309.
4
the Department of Biology, Illinois Institute of Technology, Chicago, Illinois 60616.
5
the Faculty of Science, University of Kragujevac, Kragujevac 34000, Serbia.
6
the Departments of Pediatrics (Cardiology) and.
7
Biochemistry, Stanford University School of Medicine, Stanford, California 94305, and.
8
From the School of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom, m.a.geeves@kent.ac.uk.
9
the BioFrontiers Institute and Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309, leslie.leinwand@Colorado.edu.

Abstract

Dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM) can cause arrhythmias, heart failure, and cardiac death. Here, we functionally characterized the motor domains of five DCM-causing mutations in human β-cardiac myosin. Kinetic analyses of the individual events in the ATPase cycle revealed that each mutation alters different steps in this cycle. For example, different mutations gave enhanced or reduced rate constants of ATP binding, ATP hydrolysis, or ADP release or exhibited altered ATP, ADP, or actin affinity. Local effects dominated, no common pattern accounted for the similar mutant phenotype, and there was no distinct set of changes that distinguished DCM mutations from previously analyzed HCM myosin mutations. That said, using our data to model the complete ATPase contraction cycle revealed additional critical insights. Four of the DCM mutations lowered the duty ratio (the ATPase cycle portion when myosin strongly binds actin) because of reduced occupancy of the force-holding A·M·D complex in the steady state. Under load, the A·M·D state is predicted to increase owing to a reduced rate constant for ADP release, and this effect was blunted for all five DCM mutations. We observed the opposite effects for two HCM mutations, namely R403Q and R453C. Moreover, the analysis predicted more economical use of ATP by the DCM mutants than by WT and the HCM mutants. Our findings indicate that DCM mutants have a deficit in force generation and force-holding capacity due to the reduced occupancy of the force-holding state.

KEYWORDS:

actin and myosin ATPase; cardiac muscle; cardiac myosin; cardiomyopathy; computer modeling; dilated cardiomyopathy; duty ratio; heart disease; human cardiomyopathy; hypertrophic cardiomyopathy; kinetic modeling; kinetics; mechanotransduction; molecular motor

PMID:
29666183
PMCID:
PMC5995530
DOI:
10.1074/jbc.RA118.001938
[Indexed for MEDLINE]
Free PMC Article

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