Glutamine synthetases of green and etiolated leaves ofSinapis alba |
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Authors: | M Höpfner G Ochs A Wild |
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Institution: | 1. Institut für Allgemeine Botanik der Johannes Gutenberg-Universit?t, Saarstrasse 21, D-6500, Mainz, Germany
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Abstract: | Studies on the glutamine synthetases (GS, EC 6.3.1.2) of green (GS2) and etiolated leaves (GSet) ofSinapis alba L. (cv. Steinacher) revealed striking similarities between the respective enzyme proteins. The enzymes showed corresponding
chromatographic properties, both on dimethylaminoethyl-Sephacel and on hydroxylapatite columns. The purified GS proteins were
also identical with regard to the molecular weight of their subunits. Isoelectrofocusing of pure GSet yielded two distinct polypeptide bands in the pH 5.6 region of the gels. This pattern corresponded to the two strong bands
of GS2. Two charge variants of GS polypeptides could be detected by Western-blot analysis of the soluble protein of green leaves
using antibodies against mustard GS2. In immunoprecipitation experiments, the holoenzymes of GS2 and GSet were recognized with identical affinities by this antiserum. We conclude that strong similarities exist between the proteins
of the GS enzymes in green and etiolated leaves of mustard. Most probably only one GS form, namely the plastidic enzyme, can
be found in the epigeal organs ofSinapis. The polypeptides of the GS2 subunits showed no differences in the hydrophobicity of the polypeptide chains. Neither glucosyl nor mannosyl residues could
be detected.
Dedicated to Professor Dr. H. Mohr on the occasion of his 60th birthday |
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Keywords: | Etiolation leaf Glutamine synthetase (purification structure) Leaf (glutamine synthetase) Sina pis (glutamine synthetase) |
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