Molecular Characterization of Glutamine Synthetase from the Nitrogen-Fixing Phototrophic Bacterium Rhodopseudomonas palustris1

Kassem Alef 1 , Hans-Joachim Burkardt 2 , Hans-Joachim Horstmann 3  and Walter G. Zumft 1
  • 1 Institut für Botanik, Schloßgarten 4
  • 2 Institut für Mikrobiologie und Biochemie, Egerlandstr. 7
  • 3 Institut für Physiologische Chemie, Fahrstraße 17, Universität Erlangen-Nürnberg, 8520 Erlangen, Bundesrepublik Deutschland

The phototrophic bacterium Rhodopseudomonas palustris assimilated ammonium via glutamine synthetase and glutamate synthase. Diazotrophic and ammonium-grown cells had high levels of both enzymes, whereas enzymes of alternative assimilatory pathways were absent or had only low activities. Glutamine synthetase was purified to electrophoretic homogeneity within three steps by dye-ligand and ion exchange chromatography. Electron microscopy revealed a dodecameric molecular entity which was in accordance with parameters derived from electrophoretic techniques. The molecular weight of the enzyme monomer was 55 800; that of the dodecamer 670 000. The amino acid composition of R. palustris glutamine synthetase was determined and compared by a statistical method with other known enzyme compositions from prokaryotic and eukaryotic origins

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A Journal of Biosciences: Zeitschrift für Naturforschung C (ZNC) is an international scientific journal for the emerging field of natural and natural-like products. ZNC publishes original research on the isolation, bio-chemical synthesis and bioactivities of natural products, their biochemistry, pharmacology, biotechnology, and biological activity and innovative developed computational methods for predicting their structure and/or function.