  F1-ATPase (or F1), the highly-efficient and reversible biochemical engine,
has motivated physicists as well as biologists to imagine the design principles
governing machines in the fluctuating world. Recent experiments have clarified
yet another interesting property of F1; the dissipative heat inside the motor
is very small, irrespective of the velocity of rotation and energy transport.
Conceptual interest is devoted to the fact that the amount of internal
dissipation is not simply determined by the sequence of equilibrium pictures,
but also relies on the rotational-angular dependence of nucleotide affinity,
which is a truly nonequilibrium aspect. We propose that the totally asymmetric
allosteric model (TASAM), where adenosine triphosphate (ATP) binding to F1 is
assumed to have low dependence on the angle of the rotating shaft, produces
results that are most consistent with the experiment. Theoretical analysis
proves the crucial role of two time scales in the model, which explains the
universal mechanism to produce the internal dissipation-free feature. The model
reproduces the characteristic torque dependence of the rotational velocity of
F1, and predicts that the internal dissipation upon the ATP synthesis direction
rotation becomes large at the low nucleotide condition.
