The nuclear pore as a thermodynamic machine

Michael Elbaum

Department of Materials and Interfaces, Faculty of Chemistry, Weizmann Institute of Science.

The cells of higher organisms divide many biochemical functions into discrete, membrane-bound organelles. This separation allows for specialization of the internal chemistry, but demands a system of cross-membrane communication. Among the cellular organelles the nucleus is the largest and most prominent. It stores the genome as DNA, and serves as the site for RNA synthesis. The final conversion of genetic code to a protein sequence takes place in the cytoplasm, however. The necessary molecular traffic takes place through the nuclear pores. Based on detailed kinetic measurements in the style of classical enzymology, we arrive at a surprisingly simple description of the nuclear pore as a substrate-specific molecular pump that relies on equilibration of a molecular intermediary. The thermodynamic behavior is physically interesting as energy dissipation is completely decoupled from the transport process per se. This paradigm may serve as a model for technological applications.