Cloning,sequencing, and characterization of a gene (narT) encoding a transport protein involved in dissimilatory nitrate reduction inStaphylococcus carnosus |
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Authors: | Beate Fast Per-Eric Lindgren Friedrich Götz |
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Institution: | (1) Mikrobielle Genetik, Universität Tübingen, Waldhäuserstrasse 70/8, D-72076 Tübingen, Germany;(2) Present address: MPI für Biochemie, Genzentrum, Am Klopferspitz 18a, D-82152 Martinsried, Germany;(3) Present address: Department of Biology, Linköping University, S-58183 Linköping, Sweden |
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Abstract: | A Tn917 mutant ofStaphylococcus carnosus TM300, nrIII, was isolated and characterized. Mutant nrIII did not take up nitrate or accumulate nitrite when grown in B-medium supplemented with up to 10 mM nitrate under anoxic conditions; however, it displayed wild-type levels of benzyl viologen-linked nitrate reductase activity. Cultivated in B-medium with nitrate under oxic conditions, mutant nrIII accumulated fivefold less nitrite than the wild-type. The mutation inS. carnosus nrIII could be complemented with a 2-kb chromosomalEcoRI-HpaI fragment from the wild-type. The gene affected by transposon insertion in mutant nrIII was cloned and sequenced. Analysis of the deduced amino acid sequence revealed that this gene, designatednarT, encodes a highly hydrophobic 42-kDa transmembrane protein of 388 amino acids and shows similarities to transport proteins that play a role in nitrate import or nitrite export. The inability of nrIII to take up nitrate under anoxic conditions and its ability to take up and accumulate nitrite in the presence of benzyl viologen, a nitrate ionophore, under the same conditions suggest that NarT represents a transport protein required for nitrate uptake under anoxic conditions inS. carnosus. |
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Keywords: | Staphylococcus carnosus Tn917 insertion mutant Nitrate uptake Nitrite export |
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