title: Site-specific alteration of cysteine 281, cysteine 344, and cysteine 349 in the proline carrier of Escherichia coli.
abstract: Cys-281, Cys-344, or Cys-349 in the proline carrier of Escherichia coli was changed to a serine residue by site-specific mutagenesis. The activities of the resultant mutants for uptake of proline were as great as that of the wild-type strain. These mutant carriers were all as sensitive as the wild-type carrier to the proline analogue azetidine 2-carboxylate. However, the mutant carriers with Ser-281 and Ser-344 were resistant to N-ethylmaleimide, whereas the mutant carrier with Ser-349 was as sensitive as the wild-type carrier to this reagent. These results indicate that these cysteine residues are not essential for proline transport and that Cys-281 and Cys-344 may be close to the substrate-binding site that contains an N-ethylmaleimide-sensitive residue.
mesh_terms: D026921:Amino Acid Transport Systems, Neutral; D001384:Azetidines / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D003545:Cysteine; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D005033:Ethylmaleimide / Q000494:pharmacology; D007700:Kinetics; D009154:Mutation; D010957:Plasmids; D011392:Proline / Q000378:metabolism*; D011487:Protein Conformation; D027981:Symporters
chemical_list: D026921:Amino Acid Transport Systems, Neutral; D001384:Azetidines; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D027981:Symporters; C041832:proline transport protein; C060609:PutP protein, E coli; D011392:Proline; D003545:Cysteine; D005033:Ethylmaleimide