  We present a model of an ATP-fueled molecular machine which push a polymer
through a pore channel. The machine acts between two levels (working-waiting),
and the working one remains active for a fixed time giving a constant force.
The machine activation rate can be put in relationship with the available ATP
concentration in the solution, which gives the necessary energy supply. The
translocation time shows a monotonic behavior as a function of the activation
frequency and the velocity follows a Michaelis-Menten law that arises naturally
in this description. The estimation of the stall force of the motor follows a
corrected Michaelis-Menten law which still is to be checked in experimental
investigation. The results presented agree with recent biological experimental
findings.
