Open AccessInvolvement of sulphydryl groups in glutamine synthetase activity from Rhodobacter capsulatus E1F1
Author(s) -
Caballero Francisco Javier,
Cárdenas Jacobo,
Castillo Francisco
Publication year - 1987
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1987.tb02132.x
Subject(s) - rhodobacter , glutamine synthetase , dithiothreitol , rhodospirillales , biochemistry , cysteine , rhodospirillaceae , glutamine , transferase , biology , protein subunit , enzyme , amino acid , gene , mutant
Glutamine synthetase (GS) from the phototrophic bacterium Rhodobacter capsulatus E1F1 (formerly known as Rhodopseudomonas capsulata E1F1) contains 9 SH‐groups per subunit. These SH‐groups reacted with sulphydryl group reagents resulting in an inhibition of the transferase activity of GS. Inhibited GS was recovered up to 90% of its initial value by treatment with thiols such as l ‐cysteine, dithiothreitol, or 2‐mercaptoethanol. However, dithioerythritol exhibited, at concentrations above 0.5 mM, a significant inhibition of the transferase activity. Glutamine and glutamate protected against the inactivation by sulphydryl group reagents, whereas ADP or ATP enhanced the velocity of inactivation considerably. Mn 2+ ‐dependent GS was unaffected in vivo by light‐dark transitions, which rules out a redox photoregulation of SH‐groups required for activity.