Functional characterization of three GlnB homologs in the photosynthetic bacterium Rhodospirillum rubrum: roles in sensing ammonium and energy status.
The GlnB (P(II)) protein, the product of glnB, has been characterized previously in the photosynthetic bacterium Rhodospirillum rubrum. Here we describe identification of two other P(II) homologs in this organism, GlnK and GlnJ. Although the sequences of these three homologs are very similar, the molecules have both distinct and overlapping functions in the cell. While GlnB is required for activation of NifA activity in R. rubrum, GlnK and GlnJ do not appear to be involved in this process. In contrast, either GlnB or GlnJ can serve as a critical element in regulation of the reversible ADP ribosylation of dinitrogenase reductase catalyzed by the dinitrogenase reductase ADP-ribosyl transferase (DRAT)/dinitrogenase reductase-activating glycohydrolase (DRAG) regulatory system. Similarly, either GlnB or GlnJ is necessary for normal growth on a variety of minimal and rich media, and any of the proteins is sufficient for normal posttranslational regulation of glutamine synthetase. Surprisingly, in their regulation of the DRAT/DRAG system, GlnB and GlnJ appeared to be responsive not only to changes in nitrogen status but also to changes in energy status, revealing a new role for this family of regulators in central metabolic regulation.
Zhang
Y
Y
Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Pohlmann
E L
EL
Ludden
P W
PW
Roberts
G P
GP
D036002:ADP Ribose Transferases / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D003001:Cloning, Molecular; D003624:Darkness; D004734:Energy Metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D009699:N-Glycosyl Hydrolases; D009243:NAD / Q000494:pharmacology; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000378:metabolism; D051922:PII Nitrogen Regulatory Proteins; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D012247:Rhodospirillum rubrum / Q000378:metabolism*
D001426:Bacterial Proteins; D002352:Carrier Proteins; C439048:GlnJ protein, Rhodospirillum rubrum; C113488:GlnK protein, Azorhizobium caulinodans; C439047:GlnK protein, Rhodospirillum rubrum; D051922:PII Nitrogen Regulatory Proteins; D000644:Quaternary Ammonium Compounds; D009243:NAD; C404143:PIID regulatory protein, Bacteria; D009591:Nitrogenase; D036002:ADP Ribose Transferases; C057637:dinitrogenase reductase ADP-ribosyltransferase; D006026:Glycoside Hydrolases; D009699:N-Glycosyl Hydrolases; C036091:ADP-ribosyl-(dinitrogen reductase) hydrolase; C081173:glutamine synthetase I; D005974:Glutamate-Ammonia Ligase