A high-affinity site for glutathione in the cytoplasm of Escherichia coli and its possible role in potassium retention.
Glutathione-deficient mutants of Escherichia coli, unlike the wild type, exhibit a fast leak and a fast turnover of K+ at steady state. In a medium with low K+ the growth rate is very slow when unsupplemented with glutathione; when supplemented with glutathione at a concentration as low as 0.1 microM the growth rate is similar to that of the wild type. The ability of glutathione to restore a wild-type growth rate can be accounted for by an immediate reduction of the K+ leak. Two analogs of glutathione also reduce the K+ leak: gamma-glutamylaminobutyrylglycine (ophthalmic acid) and alpha gamma-glutamylcystinylbisglycine. Glutathione binds with high affinity (Kd 50 nM) to a cytoplasmic protein; ophthalmic acid and alpha gamma-glutamylcystinylbisglycine compete with glutathione for the binding site (Ki 0.1 microM and 1 microM), thereby ruling out the possibility that the thiol is involved both in reducing the K+ leak and in binding to the high affinity binding site. For each of the three peptides the Kd for binding is similar to the minimal concentration that achieves the maximal reduction of the K+ leak. The results suggest that the binding of glutathione should play a role in the retention of K+ in E. coli.
Meury
J
J
Robin
A
A
D001426:Bacterial Proteins / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D005978:Glutathione / Q000172:deficiency / Q000502:physiology; D009154:Mutation; D011188:Potassium / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018000:Receptors, Peptide
D001426:Bacterial Proteins; D011956:Receptors, Cell Surface; D018000:Receptors, Peptide; C035560:glutathione receptor; D005978:Glutathione; D011188:Potassium