title: The role of cysteine residues in the transport of mercuric ions by the Tn501 MerT and MerP mercury-resistance proteins.
abstract: Each cysteine residue in the MerT and MerP polypeptides of bacterial transposon Tn501 was replaced by serine, and the mercury-resistance phenotypes of the mutants were determined in Escherichia coli. Cys-24 and Cys-25 in the first transmembrane region of MerT were essential for transport of mercuric ions through the cytoplasmic membrane, and mutations Cys-76-Ser, Cys-82-Ser or Gly-38-Asp in MerT or Cys-36-Ser in MerP all reduced transport and resistance. Deletion of the merP gene slightly reduced mercuric ion resistance and transport, whereas a Cys-33-Ser mutation in MerP appears to block transport of mercuric ions by MerT. The effects of deleting merP on mutations in merT were tested. The 116-amino-acid MerT protein is sufficient for mercuric ion transport across the cytoplasmic membrane.
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D027682:Cation Transport Proteins; D002462:Cell Membrane / Q000737:chemistry; D003545:Cysteine / Q000502:physiology*; D003593:Cytoplasm / Q000378:metabolism; D004251:DNA Transposable Elements / Q000502:physiology; D004352:Drug Resistance, Microbial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D017136:Ion Transport; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008627:Mercuric Chloride / Q000378:metabolism* / Q000494:pharmacology; D008969:Molecular Sequence Data; D009154:Mutation; D009876:Operon / Q000235:genetics; D010088:Oxidoreductases / Q000502:physiology; D011506:Proteins; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D004251:DNA Transposable Elements; D008565:Membrane Proteins; C086060:MerP protein, Bacteria; D011506:Proteins; C094115:mercury transport protein, bacterial; D008627:Mercuric Chloride; D010088:Oxidoreductases; C021551:mercuric reductase; D003545:Cysteine