Identification of critical residues in GlnB for its activation of NifA activity in the photosynthetic bacterium Rhodospirillum rubrum
AUTOR(ES)
Zhang, Yaoping
FONTE
National Academy of Sciences
RESUMO
The PII regulatory protein family is unusually widely distributed, being found in all three domains of life. Three PII homologs called GlnB, GlnK, and GlnJ have been identified in the photosynthetic bacterium Rhodospirillum rubrum. These have roles in at least four distinct functions, one of which is activation of the nitrogen fixation-specific regulatory protein NifA. The activation of NifA requires only the covalently modified (uridylylated) form of GlnB. GlnK and GlnJ are not involved. However, the basis of specificity for different PII homologs in different processes is poorly understood. We examined this specificity by altering GlnJ to support NifA activation. A small number of amino acid substitutions in GlnJ were important for this ability. Two (affecting residues 45 and 54) are in a loop called the T-loop, which contains the site of uridylylation and is believed to be very important for contacts with other proteins, but other critical residues lie in the C terminus (residues 95–97 and 109–112) and near the N terminus (residues 3–5 and 17). Because many of the residues important for PII–NifA interaction lie far from the T-loop in the known x-ray crystal structures of PII proteins, our results lead to the hypothesis that the T-loop of GlnB is flexible enough to come into proximity with both the C- and N-terminal regions of the protein to bind NifA. Finally, the results show that the level of PII accumulation is also an important factor for NifA activation.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=365697Documentos Relacionados
- Mutagenesis and Functional Characterization of the glnB, glnA, and nifA Genes from the Photosynthetic Bacterium Rhodospirillum rubrum
- 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
- Functional Characterization of Three GlnB Homologs in the Photosynthetic Bacterium Rhodospirillum rubrum: Roles in Sensing Ammonium and Energy Status
- Effect of ATP and 2-oxoglutarate on the in vitro interaction between the NifA GAF domain and the GlnB protein of Azospirillum brasilense
- Role of GlnK in NifL-Mediated Regulation of NifA Activity in Azotobacter vinelandii