Abstract : ABSTRACT: In order to determine the energy consumption during transitions between critical conformational states of myosin S1, molecular mechanics and dynamics simulations were applied to native myosin S1 structure. Dynamics simulations on the myosin S1 motor domain indicated that significant flexibility was present throughout the molecular model. The conformational transition is induced using a spring constant of 16.7 N/m. A simulated force-distance curve is calculated based on the difference between the actual distance and target distance after successive energy minimizations and the area under the force distance plot is determined. Analysis of different conformational states provided new insights into energy consumption in myosin S1 and molecular level details of the complex internal interactions of myosin. Cross linking reactive cysteines SH1 and SH2 with nucleotide binding site closed/open are consistent with experimental studies. Energy consumption is maximum when SH1 SH2 reactive cysteines are crosslinked with nucleotide binding site open. KEYWORDS: Myosin, Molecular motors, Energy minimization, Molecular dynamic simulations, Conformations, RMSD(Root mean square deviations).