The role of GlnD in ammonia assimilation in Mycobacterium tuberculosis.
The control of ammonia assimilation in Mycobacterium tuberculosis is poorly understood. We have been investigating a regulatory cascade predicted to control the activity of glutamine synthetase (GS). We previously demonstrated that the GS-modifying protein, GlnE (an adenylyl transferase), is essential for M. tuberculosis growth. GlnD, a uridylyl transferase, is involved in the control of GlnE activity in other bacteria. In M. tuberculosis, glnD is arranged in an apparent operon with amt and glnB; all three genes are up-regulated in a low-ammonia medium. We constructed an in-frame deletion of glnD by homologous recombination. The mutant had no growth defect in media containing different nitrogen sources. Total GS activity in culture filtrates was markedly reduced in the mutant, although activity in cell-free extracts remained normal. Virulence was unaffected in both in vitro and in vivo model systems of infection, indicating that the presence of extra-cellular GS is not critical for virulence and that the residual intra-cellular GS activity is sufficient. Thus although GlnD does play a role in the control of ammonia assimilation, it is not required for virulence.
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Rose
R
Centre for Infectious Disease, Institute for Cell and Molecular Science, Barts and the London, 4 Newark Street, London E1 2AT, UK.
Pashley
Carey A
CA
Smith
Debbie
D
Parish
Tanya
T
D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D002384:Catalysis; D005798:Genes, Bacterial / Q000502:physiology*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D066298:In Vitro Techniques; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D016513:Mice, SCID; D050505:Mutant Proteins; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion; D014774:Virulence
D050505:Mutant Proteins; D000641:Ammonia; D005974:Glutamate-Ammonia Ligase