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Structural gene for NAD synthetase in Salmonella typhimurium
K T Hughes1, B M Olivera, J R Roth
1Department of Biology, University of Utah, Salt Lake City 84112.
Journal of Bacteriology
|May 1, 1988
Summary
Researchers identified the NAD synthetase gene (nadE) in Salmonella typhimurium, crucial for NAD biosynthesis. Mutants accumulate substrate, and the enzyme appears multimeric, with cross-species subunit interaction observed.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Nicotinamide adenine dinucleotide (NAD) is essential for cellular metabolism.
- NAD biosynthesis involves multiple enzymatic steps, with NAD synthetase catalyzing the final reaction.
Purpose of the Study:
- To identify the structural gene encoding NAD synthetase in Salmonella typhimurium.
- To characterize the genetic locus and functional properties of NAD synthetase.
Main Methods:
- Gene mapping on the Salmonella typhimurium chromosome.
- Construction and analysis of temperature-sensitive mutants.
- Biochemical assays to measure substrate accumulation.
- Native gel electrophoresis to assess enzyme subunit composition.
Main Results:
- The structural gene for NAD synthetase was identified and designated nadE, located at 27 min on the S. typhimurium chromosome.
- nadE mutants exhibited a temperature-sensitive lethal phenotype and accumulated nicotinic acid adenine dinucleotide.
- Native gel electrophoresis indicated that NAD synthetase is a multimeric enzyme composed of at least two subunits.
- Active heteromultimers formed when subunits from Escherichia coli and S. typhimurium were combined.
Conclusions:
- The nadE gene is essential for NAD biosynthesis in S. typhimurium.
- NAD synthetase is a multimeric enzyme, and its subunits show functional compatibility between different bacterial species.