生体膜のATP 合成機構

抄録

All living organisms on the earth rely solely on a single molecule as an energy currency, ATP (adenosine triphosphate). This small molecule supports nearly all the activities that require energy, and our body synthesizes roughly as much ATP every day as our body weight. In the biological world, ATP synthesis is certainly the most prevalent chemical reaction and the enzyme, ATP synthase, responsible for most of this task, is one of the most ubiquitous, abundant proteins on the earth. ATP synthase uses physical rotation of its own subunits as a step of catalysis － a novel mechanism, different from any other known enzymes. Rotation is not a favourite motion in living organisms; there is no animal with wheels, no bird with a propeller, and no fish with a screw. The crystal structures of the main part of ATP synthase show in atomic detail how the appearance of this world tiniest motor made of protein is remarkably reminiscent of the man–made motors. The driving force that spins ATP synthase is trans-membrane gradient of hydrogen ion concentration that is generated by respiration (burning the food) or by sunshine. We have videoimaged the rotary motion of ATP synthase that spins as fast as several hundred revolutions per second. The mechanism of the motor is completely different from the man–made motor. ATP synthase is bi–particle structure with a common rotary shaft. The flow of hydrogen ions through the lower particle drives the rotation of the central rotor that then forces upper particle to make the bending motion for synthesis of ATP. Imagine billions of billion rotary motors are spinning in our body, day and night, without rest. When the motors stop, we die.