Reversible control of F1-ATPase rotational motion using a photochromic ATP analog at the single molecule level

Motor enzymes such as F₁-ATPase and kinesin utilize energy from ATP for their motion. Molecular motions of these enzymes are critical to their catalytic mechanisms and were analyzed thoroughly using a single molecule observation technique. As a tool to analyze and control the ATP-driven motor enzyme motion, we recently synthesized a photoresponsive ATP analog with a p-tert-butylazobenzene tethered to the 2′ position of the ribose ring. Using cis/trans isomerization of the azobenzene moiety, we achieved a successful reversible photochromic control over a kinesin-microtubule system in an in vitro motility assay. Here we succeeded to control the hydrolytic activity and rotation of the rotary motor enzyme, F₁-ATPase, using this photosensitive ATP analog. Subsequent single molecule observations indicated a unique pause occurring at the ATP binding angle position in the presence of cis form of the analog.