Purification and structural properties of adenylylated and deadenylylated glutamine synthetase from Rhodopseudomonas sphaeroides |
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Authors: | Harald Engelhardt Jobst-Heinrich Klemme |
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Institution: | (1) Institut für Mikrobiologie der Universität, Meckenheimer Allee 168, D-5300 Bonn 1, Federal Republic of Germany;(2) Present address: Max-Planck-Institut für Biochemie, D-8033 Martinsried bei München, Federal Republic of Germany |
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Abstract: | Glutamine synthetase (GS) of Rhodopseudomonas sphaeroides is regulated by adenylylation and deadenylylation. The extent of adenylylation/deadenylylation of the enzyme in cell free extracts was influenced by inorganic phosphate (P
i), -ketoglutarate, ATP and other nucleotides. While P
i and -ketoglutarate stimulated deadenylylation, ATP and other nucleotides enhanced adenylylation of the GS. By using proper combinations of the effectors and incubation conditions, any desired adenylylation state of GS could be adjusted in vitro. The enzyme was purified to electrophoretic homogenity by three steps including affinity chromatography on 5-AMP-Sepharose. Adenylylated and deadenylylated enzyme showed different UV-spectra and isoelectric points. The native enzyme had a molecular weight of 600,000, deadenylylated subunits of 50,000±1,000. Electron microscopic investigations revealed a dodecameric arrangement of subunits in two hexameric planes. |
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Keywords: | Glutamine synthetase Deadenylylation/adenylylation in vitro Structural properties Rhodopseudomonas sphaeroides |
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