title: Two proline porters in Escherichia coli K-12.
abstract: Escherichia coli mutants defective at putP and putA lack proline transport via proline porter I and proline dehydrogenase activity, respectively. They retain a proline uptake system (proline porter II) that is induced during tryptophan-limited growth and are sensitive to the toxic L-proline analog, 3,4-dehydroproline. 3,4-Dehydroproline-resistant mutants derived from a putP putA mutant lack proline porter II. Auxotrophic derivatives derived from putP+ or putP bacteria can grow if provided with proline at low concentration (25 microM); those derived from the 3,4-dehydroproline-resistant mutants require high proline for growth (2.5 mM). We conclude that E. coli, like Salmonella typhimurium, possesses a second proline porter that is inactivated by mutations at the proP locus.
mesh_terms: D026921:Amino Acid Transport Systems, Neutral; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005798:Genes, Bacterial; D005838:Genotype; D007527:Isoenzymes / Q000235:genetics*; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000235:genetics*; D009154:Mutation; D011392:Proline / Q000378:metabolism; D013045:Species Specificity
chemical_list: D026921:Amino Acid Transport Systems, Neutral; D007527:Isoenzymes; D026901:Membrane Transport Proteins; C033082:proline transporter; D011392:Proline