  Multiple experiments show that various submicron particles such as
magnetosomes, RNA messengers, viruses, and even much smaller nanoparticles such
as globular proteins diffuse anomalously slow in viscoelastic cytosol of living
cells. Hence, their sufficiently fast directional transport by molecular motors
such as kinesins is crucial for the cell operation. It has been shown recently
that the traditional flashing Brownian ratchet models of molecular motors are
capable to describe both normal and anomalous transport of such subdiffusing
cargos by molecular motors with a very high efficiency. This work elucidates
further an important role of mechanochemical coupling in such an anomalous
transport. It shows a natural emergence of a perfect subdiffusive ratchet
regime due to allosteric effects, where the random rotations of a "catalytic
wheel" at the heart of the motor operation become perfectly synchronized with
the random stepping of a heavily loaded motor, so that only one ATP molecule is
consumed at each motor step along microtubule on average. However, the number
of rotations made by the catalytic engine and the traveling distance both scale
sublinearly in time. Nevertheless, this anomalous transport can be very fast in
absolute terms.
