PMID:15687189

Citation	Zhang, Y, Pohlmann, EL and Roberts, GP (2005) GlnD is essential for NifA activation, NtrB/NtrC-regulated gene expression, and posttranslational regulation of nitrogenase activity in the photosynthetic, nitrogen-fixing bacterium Rhodospirillum rubrum. J. Bacteriol. 187:1254-65
Abstract	GlnD is a bifunctional uridylyltransferase/uridylyl-removing enzyme and is thought to be the primary sensor of nitrogen status in the cell. It plays an important role in nitrogen assimilation and metabolism by reversibly regulating the modification of P(II) proteins, which in turn regulate a variety of other proteins. We report here the characterization of glnD mutants from the photosynthetic, nitrogen-fixing bacterium Rhodospirillum rubrum and the analysis of the roles of GlnD in the regulation of nitrogen fixation. Unlike glnD mutations in Azotobacter vinelandii and some other bacteria, glnD deletion mutations are not lethal in R. rubrum. Such mutants grew well in minimal medium with glutamate as the sole nitrogen source, although they grew slowly with ammonium as the sole nitrogen source (MN medium) and were unable to fix N(2). The slow growth in MN medium is apparently due to low glutamine synthetase activity, because a DeltaglnD strain with an altered glutamine synthetase that cannot be adenylylated can grow well in MN medium. Various mutation and complementation studies were used to show that the critical uridylyltransferase activity of GlnD is localized to the N-terminal region. Mutants with intermediate levels of uridylyltransferase activity are differentially defective in nif gene expression, the posttranslational regulation of nitrogenase, and NtrB/NtrC function, indicating the complexity of the physiological role of GlnD. These results have implications for the interpretation of results obtained with GlnD in many other organisms.
Links	PubMed PMC545621 Online version:10.1128/JB.187.4.1254-1265.2005
Keywords	Ammonia/metabolism; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Culture Media/chemistry; DNA Mutational Analysis; Gene Deletion; Gene Expression Regulation, Bacterial; Genetic Complementation Test; Glutamate Synthase/genetics; Glutamate Synthase/metabolism; Glutamic Acid/metabolism; Nitrogen/metabolism; Nitrogen Fixation; Nitrogenase/metabolism; Nucleotidyltransferases/genetics; Nucleotidyltransferases/metabolism; PII Nitrogen Regulatory Proteins; Protein Structure, Tertiary; Rhodospirillum rubrum/enzymology; Rhodospirillum rubrum/genetics; Rhodospirillum rubrum/growth & development; Rhodospirillum rubrum/metabolism; Sequence Deletion; Transcription Factors/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
RHORT:GLND	involved_in	GO:0018177: protein uridylylation	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
RHORT:GLND	involved_in	GO:0090293: nitrogen catabolite regulation of transcription	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
RHORT:GLND		GO:0090293: nitrogen catabolite regulation of transcription	ECO:0000315:		P		Table 2 shows that the presence of N-terminal region of GlnD allows glnD mutant R.rubrum to have nitrogenase activity via NifA activation.	complete CACAO 8701
RHORT:GLND		GO:0018177: protein uridylylation	ECO:0000315:		P		Table 3 shows the impact of glnD mutation on the ability of mutant R.rubrum to recover its nitrogenase activity via GlnB and GlnJ uridylylation after returning to light.	complete CACAO 8702
RHORT:GLND		GO:0008773: [protein-PII] uridylyltransferase activity	ECO:0000315:		F		Fig 5 shows that no GlnJ protein was synthesized in glnD mutant R.rubrum.	complete CACAO 8703
RHORT:GLND		GO:0045893: positive regulation of transcription, DNA-templated	ECO:0000315:		P		Figure 5 shows that no GlnJ protein was synthesized in glnD mutant R.rubrum	complete CACAO 8835
RHORT:GLND	involved_in	GO:0045893: positive regulation of transcription, DNA-templated	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

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