Modification of glutamine synthetase in Streptomyces griseus by ADP-ribosylation and adenylylation.
Addition of NH4+ to STreptomyces griseus 2682 cells grown in NO3- containing medium resulted in a rapid decline in glutamine synthetase activity due to covalent modification of the enzyme. The NH4+ promoted inactivation of the enzyme was inhibited by the ADP-ribosyltransferase inhibitor 3-methoxybenzamide. In the presence of ADP-ribosyltransferase activity the purified glutamine synthetase was also inhibited by NAD+ in a concentration-dependent manner. ADP-ribosylation of glutamine synthetase was demonstrated in vitro by showing the incorporation of labeled ADP-ribose from [alpha-32P]NAD+ into glutamine synthetase subunits. Beside ADP-ribosylation, adenylylation of glutamine synthetase was also shown in S. griseus since phosphodiesterase I treatment reactivated the enzyme in crude extracts of NH(4+)-shocked cells. Glutamine synthetase was also inhibited and modified by ATP in crude cellular extracts. These results suggest that in S. griseus 2682 ADP-ribosylation of glutamine synthetase could be an alternative modification to adenylylation to regulate glutamine synthetase activity.
Department of Biology, University Medical School Debrecen, Hungary.
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Penyige
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Kálmánczhelyi
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Sipos
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Barabás
D000228:Adenine Phosphoribosyltransferase / Q000037:antagonists & inhibitors; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D005974:Glutamate-Ammonia Ligase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D013305:Streptomyces griseus / Q000201:enzymology*
D000644:Quaternary Ammonium Compounds; D000246:Adenosine Diphosphate Ribose; D000255:Adenosine Triphosphate; D000228:Adenine Phosphoribosyltransferase; D005974:Glutamate-Ammonia Ligase