Regulation of glutamate metabolism by protein kinases in mycobacteria.
Protein kinase G of Mycobacterium tuberculosis has been implicated in virulence and in regulation of glutamate metabolism. Here we show that this kinase undergoes a pattern of autophosphorylation that is distinct from that of other M. tuberculosis protein kinases characterized to date and we identify GarA as a substrate for phosphorylation by PknG. Autophosphorylation of PknG has little effect on kinase activity but promotes binding to GarA, an interaction that is also detected in living mycobacteria. PknG phosphorylates GarA at threonine 21, adjacent to the residue phosphorylated by PknB (T22), and these two phosphorylation events are mutually exclusive. Like the homologue OdhI from Corynebacterium glutamicum, the unphosphorylated form of GarA is shown to inhibit alpha-ketoglutarate decarboxylase in the TCA cycle. Additionally GarA is found to bind and modulate the activity of a large NAD(+)-specific glutamate dehydrogenase with an unusually low affinity for glutamate. Previous reports of a defect in glutamate metabolism caused by pknG deletion may thus be explained by the effect of unphosphorylated GarA on these two enzyme activities, which may also contribute to the attenuation of virulence.
O'Hare
Helen M
HM
Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland. hmo7@le.ac.uk
Durán
Rosario
R
Cerveñansky
Carlos
C
Bellinzoni
Marco
M
Wehenkel
Anne Marie
AM
Pritsch
Otto
O
Obal
Gonzalo
G
Baumgartner
Jens
J
Vialaret
Jérome
J
Johnsson
Kai
K
Alzari
Pedro M
PM
D000595:Amino Acid Sequence; D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D008969:Molecular Sequence Data; D020102:Mycobacterium smegmatis / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*
D018698:Glutamic Acid; D005969:Glutamate Dehydrogenase; C475060:PknB protein, Mycobacterium tuberculosis; D017346:Protein Serine-Threonine Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D002262:Carboxy-Lyases; C021474:2-oxoglutarate decarboxylase