کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
10537236 | 962699 | 2013 | 9 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
A novel arsenate reductase from the bacterium Thermus thermophilus HB27: Its role in arsenic detoxification
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی آنالیزی یا شیمی تجزیه
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چکیده انگلیسی
Microorganisms living in arsenic-rich geothermal environments act on arsenic with different biochemical strategies, but the molecular mechanisms responsible for the resistance to the harmful effects of the metalloid have only partially been examined. In this study, we investigated the mechanisms of arsenic resistance in the thermophilic bacterium Thermus thermophilus HB27. This strain, originally isolated from a Japanese hot spring, exhibited tolerance to concentrations of arsenate and arsenite up to 20 mM and 15 mM, respectively; it owns in its genome a putative chromosomal arsenate reductase (TtarsC) gene encoding a protein homologous to the one well characterized from the plasmid pI258 of the Gram + bacterium Staphylococcus aureus. Differently from the majority of microorganisms, TtarsC is part of an operon including genes not related to arsenic resistance; qRT-PCR showed that its expression was four-fold increased when arsenate was added to the growth medium. The gene cloning and expression in Escherichia coli, followed by purification of the recombinant protein, proved that TtArsC was indeed a thioredoxin-coupled arsenate reductase with a kcat/KM value of 1.2 Ã 104 Mâ 1 sâ 1. It also exhibited weak phosphatase activity with a kcat/KM value of 2.7 Ã 10â 4 Mâ 1 sâ 1. The catalytic role of the first cysteine (Cys7) was ascertained by site-directed mutagenesis. These results identify TtArsC as an important component in the arsenic resistance in T. thermophilus giving the first structural-functional characterization of a thermophilic arsenate reductase.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics - Volume 1834, Issue 10, October 2013, Pages 2071-2079
Journal: Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics - Volume 1834, Issue 10, October 2013, Pages 2071-2079
نویسندگان
Immacolata Del Giudice, Danila Limauro, Emilia Pedone, Simonetta Bartolucci, Gabriella Fiorentino,