Related Experiment Videos
The ATPase activity of subfragment-1 from the hypertrophied heart
Insights
Cardiac hypertrophy in rabbits reduced myosin’s Ca2+-stimulated ATPase activity. This suggests altered myosin function in hypertrophied hearts, impacting cardiac muscle performance.
Area of Science:
- Biochemistry
- Cardiology
- Molecular Biology
Background:
- Cardiac hypertrophy is an adaptive response to increased workload.
- Myosin is a key motor protein in cardiac muscle contraction.
- Alterations in myosin function can lead to heart dysfunction.
Purpose of the Study:
- To investigate changes in myosin and subfragment-1 (S-1) ATPase activity in rabbit hearts with hypertrophy.
- To understand the functional consequences of myosin alterations in cardiac hypertrophy.
Main Methods:
- Myosin and S-1 were isolated from rabbit hearts with induced hypertrophy and control hearts.
- Calcium-stimulated and potassium/EDTA-stimulated ATPase activities were measured.
- Actin-stimulated ATPase activity of S-1 was assessed.
Main Results:
- Ca2+-stimulated ATPase activity of both myosin and S-1 was reduced in hypertrophied hearts.
- Potassium/EDTA-stimulated ATPase activity remained unchanged.
- Actin-stimulated ATPase activity of hypertrophy S-1 showed a slight, non-significant depression.
Conclusions:
- Hypertrophy alters myosin's Ca2+-dependent ATPase function, suggesting impaired contractility.
- Papain cleavage might mask conformational differences between control and hypertrophy myosins.
Abstract:
Myosin and subfragment-1 were prepared from rabbit hearts hypertrophied secondary to pulmonary artery constriction. The Ca2+ -stimulated ATPase activity was reduced while the potassium/EDTA-stimulated ATPase activity was unchanged in both the myosin and subfragment 1 (S-1) from hypertrophied hearts. When hypertrophy myosin was mixed with an equal quantity of control myosin, the ATPase activity of the mixed protein fell halfway between control and hypertrophy values. Similar results were obtained with control and hypertrophy S-1. The actin-stimulated ATPase activity of hypertrophy S-1 was slightly depressed but unlike hypertrophy myosin this depression was not significant when compared to normal S-1. This suggests that papain cleavage may have removed part of the conformational difference that exists between control and hypertrophy myosins.