ISSN:
1573-2657
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract Familial hypertrophic cardiomyopathy (FHC) is a disease of the sarcomere. In the β-myosin heavy chain gene, which codes for the mechanical enzyme myosin, greater than 40 point mutations have been found that are causal for this disease. We have studied the effect of two mutations, the R403Q and L908V, on myosin molecular mechanics. In the in vitro motility assay, the mutant myosins produced a 30% greater velocity of actin filament movement (νactin). At the single molecule level, νactin ∼d/t on, where d is the myosin unitary step displacement and t on is the step duration. Laser trap studies were performed at 10 μM MgATP to estimate d and t on for the normal and mutant myosin molecules. The increase in νactin can be explained by a significant decrease in the average t on's in both the R403Q and L908V mutants (∼30 ms) compared to controls (∼40 ms), while d was not different for all myosins tested (∼7 nm). Thus the mutations affect the kinetics of the cross-bridge cycle without any effect on myosin's inherent motion and force generating capacity. Based on these studies, the primary signal for the hypertrophic response appears to be an apparent gain in function of the individual mutant myosin molecules.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1005678905119
Permalink