Simultaneous measurement of individual ATPase and mechanical reactions by a single myosin molecule at work

Based on techniques for single molecule imaging and nanomanipulation by opt ical tweezers, we have developed a new technique that allows simultaneous m easurement of individual ATPase and mechanical reactions from a single myos in molecule during force generation. We show how the ATPase reaction couple s to the mechanical reaction directly at the single molecule level. The res ults show that the myosin head can produce force even after releasing the b ound nucleotide, probably ADP, suggesting that the chemical energy driven b y ATP hydrolysis can be hysteretically stored in the myosin molecule. This view does not support a widely accepted hypothesis in which the force gener ation is tightly coupled to ligand dissociation.