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.