A novel histidine-rich CPx-ATPase from the filamentous cyanobacterium Oscillatoria brevis related to multiple-heavy-metal cotolerance.
A novel gene related to heavy-metal transport was cloned and identified from the filamentous cyanobacterium Oscillatoria brevis. Sequence analysis of the gene (the Bxa1 gene) showed that its product possessed high homology with heavy-metal transport CPx-ATPases. The CPC motif, which is proposed to form putative cation transduction channel, was found in the sixth transmembrane helix. However, instead of the CXXC motif that is present in the N termini of most metal transport CPx-ATPases, Bxa1 contains a unique Cys-Cys (CC) sequence element and histidine-rich motifs as a putative metal binding site. Northern blotting and real-time quantitative reverse transcription-PCR showed that expression of Bxa1 mRNA was induced in vivo by both monovalent (Cu(+) and Ag(+)) and divalent (Zn(2+) and Cd(2+)) heavy-metal ions at similar levels. Experiments on heavy-metal tolerance in Escherichia coli with recombinant Bxa1 demonstrated that Bxa1 conferred resistance to both monovalent and divalent heavy metals. This is the first report of a CPx-ATPase responsive to both monovalent and divalent heavy metals.
Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan.
Liu
L
Tong
Susumu
S
Nakashima
Mineo
M
Shibasaka
Maki
M
Katsuhara
Kunihiro
K
Kasamo
D000251:Adenosine Triphosphatases / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D001692:Biological Transport; D000458:Cyanobacteria / Q000201:enzymology* / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D006639:Histidine / Q000737:chemistry; D019216:Metals, Heavy / Q000378:metabolism / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic
D019216:Metals, Heavy; D006639:Histidine; D000251:Adenosine Triphosphatases