Nitrogen and carbon regulation of glutamine synthetase and glutamate synthase in Corynebacterium glutamicum ATCC 13032.
The effect of nitrogen and carbon status on the regulation of glutamine synthetase (GS) and glutamate synthase (GOGAT) were investigated in Corynebacterium glutamicum 13032. Under carbon-sufficient, nitrogen-limiting conditions, GS and GOGAT activities were five- and seven-fold higher, respectively, and transcription of the corresponding genes (glnA and gltBD) was similarly induced. GS activity was also induced in complete medium with added glucose, while GOGAT activity was unaffected. Under carbon-limiting, nitrogen-limiting conditions, the level of GS induction was reduced approximately three-fold, whereas GOGAT activity did not respond. Disruption of the hkm gene, encoding a putative histidine kinase upstream of gltBD, reduced the levels of GOGAT activity two-fold under both nitrogen-rich and nitrogen-limiting conditions. Promoter studies using a hkm-chloramphenicol acetylase fusion plasmid revealed that transcription of hkm is moderately induced (ca. 1.5-fold) by nitrogen starvation, indicating that the Hkm protein may play a role in signal transduction of the nutritional status of the growth medium.
Schulz
A A
AA
Department of Molecular and Cell Biology, University of Cape Town, 7700, Cape Town, South Africa.
Collett
H J
HJ
Reid
S J
SJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D002244:Carbon; D003352:Corynebacterium / Q000201:enzymology* / Q000235:genetics; D003470:Culture Media; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D005798:Genes, Bacterial; D005970:Glutamate Synthase / Q000378:metabolism*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D000071677:Histidine Kinase; D008969:Molecular Sequence Data; D009584:Nitrogen; D011494:Protein Kinases / Q000235:genetics; D016415:Sequence Alignment; D015398:Signal Transduction; D014158:Transcription, Genetic
D003470:Culture Media; D002244:Carbon; D005970:Glutamate Synthase; D011494:Protein Kinases; D000071677:Histidine Kinase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen