title: Single molecule detection approach to muscle study: kinetics of a single cross-bridge during contraction of muscle.
abstract: D166V point mutation in the ventricular myosin regulatory light chain (RLC) is one of the causes of familial hypertrophic cardiomyopathy (FHC). We show here that the rates of cross-bridge attachment and dissociation are significantly different in isometrically contracting cardiac myofibrils from right ventricle of WT and Tg-D166V mice. To avoid averaging over ensembles of molecules composing muscle fibers, the data was collected from a single molecule. Kinetics were derived by tracking the orientation of a single actin molecule by fluorescence anisotropy. Orientation oscillated between two states, corresponding to the actin-bound and actin-free states of the myosin cross-bridge. The cross-bridge in a wild-type (healthy) heart stayed attached and detached from thin filament on average for 0.7 and 2.7 s, respectively. In FHC heart, these numbers increased to 2.5 and 5.8 s, respectively. These findings suggest that alterations in myosin cross-bridge kinetics associated with D166V mutation of RLC ultimately affect the ability of a heart to efficiently pump the blood.
authors.affiliation: Department of Molecular Biology and Immunology, Center for Commercialization of Fluorescence Technologies, University of North Texas Health Science Center, Fort Worth, TX, USA. jborejdo@hsc.unt.edu
authors.forename: Julian
authors.initials: J
authors.lastname: Borejdo
authors.forename: Danuta
authors.initials: D
authors.lastname: Szczesna-Cordary
authors.forename: Priya
authors.initials: P
authors.lastname: Muthu
authors.forename: Prasad
authors.initials: P
authors.lastname: Metticolla
authors.forename: Rafal
authors.initials: R
authors.lastname: Luchowski
authors.forename: Zygmunt
authors.initials: Z
authors.lastname: Gryczynski
authors.forename: Ignacy
authors.initials: I
authors.lastname: Gryczynski
mesh_terms: D000818:Animals; D024741:Cardiomyopathy, Hypertrophic, Familial / Q000503:physiopathology; D005454:Fluorescence Polarization / Q000379:methods*; D007700:Kinetics; D051379:Mice; D008822:Mice, Transgenic; D009119:Muscle Contraction / Q000502:physiology*; D009132:Muscles / Q000502:physiology*; D009200:Myocardial Contraction; D009206:Myocardium; D009210:Myofibrils / Q000502:physiology