  Knotted proteins, when forced through the pores, can get stuck if the knots
in their backbone tighten under force. Alternatively, the knot can slide off
the chain, making translocation possible. We construct a simple energy
landscape model of this process with a time-periodic potential that mimics the
action of a molecular motor. We calculate the translocation time as a function
of the period of the pulling force, discuss the asymptotic limits and
biological relevance of the results.
