nasST, two genes involved in the induction of the assimilatory nitrite—nitrate reductase operon (nasAB) of Azotobacter vinelandii

作者：Juan Carlos Gutiérrez, Francisco Ramos, Ludwig Ortner, Marı́a Tortolero · 发表于：Molecular Microbiology · 年份：1995 · DOI：10.1111/j.1365-2958.1995.mmi_18030579.x · 被引用次数：42 · 研究领域：Wastewater Treatment and Nitrogen Removal、Plant nutrient uptake and metabolism、Nitric Oxide and Endothelin Effects

An operon including two new genes (nasS and nasT) has been defined, cloned and sequenced. The deduced NASS protein is homologous to NRTA from Synechococcus sp. and to NASF from Klebsiella pneumoniae, two proteins involved in nitrate uptake. The predicted NAST polypeptide is homologous to the regulator proteins of the two-component regulatory systems. NASS plays a negative regulatory role in the synthesis of the nitrate and nitrite reductase. NAST is required for the expression of the nitrite-nitrate reductase operon (nasAB). Expression of the nasST operon is not under the control of the NTR system and is not regulated by the nitrogen source. A Phi(nasA-lacZ) fusion has been used to analyse expression of the nasAB operon in three different genetic backgrounds with altered nitrate reductase activity. Beta-galactosidase activity in two of them was independent of nitrate but in a mutant unable to reduce nitrate, nas-4, it was normally induced by nitrate.