Escherichia coli possesses three distinct formate dehydrogenase enzymes encoded by the fdnGHI, fdhF, and fdoGHI operons. To examine how two of the formate dehyrogenase operons (fdnGHI and fdhF) are expressed anaerobically in the presence of low, intermediate, and high levels of nitrate, nitrite, and formate, chemostat culture techniques were employed with fdnG-lacZ and fdhF-lacZ reporter fusion...

Nitrate and nitrite are preferred respiration oxidants during anaerobic conditions. In Escherichia coli such nitrate- and nitrite respiration is controlled by homologous transcriptional factors NarL and NarP. Although this system was intensively studied during the last two decades, the exact mechanisms of regulation and the structure of the NarL binding signals remained elusive. By the use of c...

Rotman lenses are attractive candidates for use in beam forming networks (BFNs) for satellitebased direct radiating arrays. This paper will review the basic design equations for a Rotman lens and will describe Rotman lens synthesis and analysis software developed by the author. The synthesis tool, named RLDESIGN, is written in MATLAB to automatically and rapidly solve the Rotman lens equations ...

The regulation of the narK gene in Escherichia coli was studied by constructing narK-lacZ gene and operon fusions and analyzing their expression in various mutant strains in response to changes in cell growth conditions. Expression of narK-lacZ was induced 110-fold by a shift to anaerobic growth and a further 8-fold by the presence of nitrate. The fnr gene product mediates this anaerobic respon...

The NarX and NarQ sensor-histidine kinases control phosphorylation of the NarL and NarP response regulators in response to the respiratory oxidants nitrate and nitrite. Target operon transcription is activated by the Fnr protein in response to anaerobiosis, and it is further activated and/or repressed by the phospho-NarL and phospho-NarP proteins, which bind to heptamer DNA sequences. The locat...

During anaerobic growth, nitrate induces synthesis of the anaerobic respiratory enzymes formate dehydrogenase-N and nitrate reductase. This induction is mediated by a transcription activator, the narL gene product. The narX gene product may be involved in sensing nitrate and phosphorylating NARL. We isolated narX mutants, designated narX*, that caused nitrate-independent expression of the forma...

Heath, T. D., Macher, B. A. & Papahadjopoulos, D. (1981) Biochim. Biophys. Actu 640, 66-81 Heath, T. D., Montgomery, J. A., Piper, J. R. & Papahadjopoulos, D. (1983) Proc. Narl. Acud. Sci. U.S.A. 80, 1377-1381 Heath, T. D., Fraley, R. T., Bentz, J., Voss, E. W. Jr., Herron, J. & Papahadjopoulos, D. (1984) Biochim. Biophys. Actu in the press Heltranu, C., Simionescu, M. & Simionescu, N. (1982) J...

NarX-NarL and NarQ-NarP are paralogous two-component regulatory systems that control Escherichia coli gene expression in response to the respiratory oxidants nitrate and nitrite. Nitrate stimulates the autophosphorylation rates of the NarX and NarQ sensors, which then phosphorylate the response regulators NarL and NarP to activate and repress target operon transcription. Here, we investigated b...