Aspartic acid-66 is the only essential negatively charged residue in the putative hydrophilic loop region of the metal-tetracycline/H+ antiporter encoded by transposon Tn10 of Escherichia coli.
Of the 16 acidic amino acid residues located in the hydrophilic region of the metal-tetracycline/H+ antiporter of transposon Tn10, five glutamic acids and three aspartic acids are conserved among the tetracycline/H+ antiporters of Gram-negative bacteria. When these conserved acidic residues were each replaced by a neutral polar residue, glutamine or asparagine, only the Asp66 substitution mutants completely lost their transport activity. The substitution of Glu274, Asp120, Glu181, or Asp38 caused significant reduction of the transport activity, whereas the substitution of the other three residues had no detectable effect on the activity. These findings led to the conclusion that only Asp66 is essential for the transport function.
Yamaguchi
A
A
Division of Microbial Chemistry, Faculty of Pharmaceutical Sciences, Chiba University, Japan.
Nakatani
M
M
Sawai
T
T
D000595:Amino Acid Sequence; D017920:Antiporters; D001224:Aspartic Acid; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002462:Cell Membrane / Q000378:metabolism; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D007700:Kinetics; D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D011487:Protein Conformation; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D013752:Tetracycline / Q000378:metabolism*; D013753:Tetracycline Resistance / Q000235:genetics*
D017920:Antiporters; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D009838:Oligodeoxyribonucleotides; D012097:Repressor Proteins; C079051:tetA protein, Bacteria; D001224:Aspartic Acid; D013752:Tetracycline