Modulation of Membrane Transport Systems

This year's theme of the section on Cell and Molecular Physiology is primarily concerned with factors that modulate membrane transport systems. The characteristics displayed by all membrane transport systems appear to be defined by intrinsic as well as extrinsic determinants. Intrinsic properties are presumably set by the amino acid sequence defining the protein/transport complex structure, while extrinsic determinants are defined by environmental interactions such as with lipids, substrates, and ligands. Most of the articles in this section deal mainly with defining extrinsic determinants because until recently these aspects have been the most experimentally accessible. However, the application of molecular biological techniques to alter transport systems offers ways to evaluate intrinsic dcterminants. As always, space limitations prevent as complete a survey as desired. Nevertheless it seems clear that combinations as well as extensions of the various approaches discussed here provide considerable insight into the molecular mechanisms that underlie the transport reactions.