Enzymatically Driven Transport: A Kinetic Theory for Nuclear Export

Nuclear import and export are often considered inverse processes whereby transport receptors ferry protein cargo through the nuclear pore. In contrast to import, where the reversible binding of receptor to nuclear RanGTP leads to a balanced bidirectional exchange, termination of export by physiologically irreversible hydrolysis of the Ran-bound GTP leads to unidirectional transport. We present a concise mathematical model that predicts protein distributions and kinetic rates for receptor-mediated nuclear export, which further exhibit an unexpected pseudolinear relation one to the other. Predictions of the model are verified with permeabilized and live cell measurements.