Ventricular myosin modifies in vitro step-size when phosphorylated

• Published in: Journal of molecular and cellular cardiology Vol. 72; pp. 231 - 237
• Main Authors: Wang, Yihua, Ajtai, Katalin, Burghardt, Thomas P
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2014
• Subjects: Actin-activated ATPase; Actins - metabolism; Adenosine Triphosphate - metabolism; Animals; Biomechanical Phenomena; Cardiac myosin RLC phosphorylation; Cardiovascular; Cell Movement; Heart Ventricles - chemistry; Heart Ventricles - metabolism; In vitro motility; Muscle, Skeletal - metabolism; Myocardial Contraction - physiology; Myocardium - metabolism; Myosin Light Chains - metabolism; Phosphorylation; Qdot assay; Quantum Dots; Rabbits; Swine; Ventricular myosin step-size; Ventricular Myosins - metabolism; smMLCK; Ventricular myosin step-size; Actin-activated ATPase; Qdot assay; RLC S15 phosphorylated βMys; RLC; Cardiac myosin ELCs (genes MYL3 or MYL4); Smooth muscle myosin light chain kinase; β cardiac myosin (gene MYL7); Cardiac myosin regulatory light chain (gene MYL2); In vitro motility; cELC; βMys; pβMys; Cardiac myosin RLC phosphorylation
• ISSN: 0022-2828; 1095-8584
• DOI: 10.1016/j.yjmcc.2014.03.022

Abstract Cardiac and skeletal muscle myosins have the central role in contraction transducing ATP free energy into the mechanical work of moving actin. Myosin has a motor domain containing ATP and actin binding sites and a lever-arm that undergoes rotation impelling bound actin. The lever-arm converts torque generated in the motor into the linear displacement known as step-size. The myosin lever-arm is stabilized by bound essential and regulatory light chains (ELC and RLC). RLC phosphorylation at S15 is linked to modified lever-arm mechanical characteristics contributing to myosin filament based contraction regulation and to the response of the muscle to disease. Myosin step-size was measured using a novel quantum dot (Qdot) assay that previously confirmed a 5 nm step-size for fast skeletal myosin and multiple unitary steps, most frequently 5 and 8 nm, and a rare 3 nm displacement for β cardiac myosin (βMys). S15 phosphorylation in βMys is now shown to change step-size distribution by advancing the 8 nm step frequency. After phosphorylation, the 8 nm step is the dominant myosin step-size resulting in significant gain in the average step-size. An increase in myosin step-size will increase the amount of work produced per ATPase cycle. The results indicate that RLC phosphorylation modulates work production per ATPase cycle suggesting the mechanism for contraction regulation by the myosin filament.