An important aspect of cell growth--how necessary nutrients get into the cell (transport)--is poorly understood in terms of ther actual molecular mechanisms of transport and the proteins responsible for it. The proline transport mutants of Salmonella will be used for studies of the molecular mechanism of sodium- driven transport. By selection for particular classes of mutants, domains of the protease involved in substrate binding and translocation will be identified; with the aid of site directed mutagenesis of the implicated residues it whould be possible to test the predicted roles of certain amino acids and come to understand, with the aid of biochemical and biophysical approaches, the conformational changes necessary for substrate translocation. Elucidation of the structure-function relationships of ion-driven transport proteins should result from such examinations.
