| Myosin light chain isoforms modify force-generating ability of cardiac myosin by changing the kinetics of actin-myosin interaction (2003) | |||||||||||||
Abstract | |||||||||||||
| Objective: To investigate the functional role of myosin light chain (MLC) isoforms in cardiac muscles, we examined the motor function of two different myosins the structure of which differed only in the MLC. Methods: We purified myosin from atria (A-myosin) and ventricles (V-myosin) of young rats, which contained atrial-type and ventricular-type MLCs, respectively, but having identical -heavy chain isoform. Actin filament velocity (Vel) was determined in the in vitro motility assay. Average force of myosin molecules (F) was estimated and single events of actin–myosin interaction were recorded with the laser trap technique. Results: Vel was slightly higher in A-myosin than in V-myosin, while actin-activated ATPase activity was not different. F, determined from force versus actin filament length relation, was 60% higher in V-myosin (3.3 vs. 2.1 pN/µm). The mean duration of isometric force events was longer in V-myosin than in A-myosin (323±13 vs. 294±30 ms, p | |||||||||||||
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