Crystal structure of nitrogen regulatory protein IIANtr from Neisseria meningitidis.
BACKGROUND
The NMB0736 gene of Neisseria meningitidis serogroup B strain MC58 encodes the putative nitrogen regulatory protein, IIANtr (abbreviated to NM-IIANtr). The homologous protein present in Escherichia coli is implicated in the control of nitrogen assimilation. As part of a structural proteomics approach to the study of pathogenic Neisseria spp., we have selected this protein for structure determination by X-ray crystallography.


RESULTS
The NM-IIANtr was over-expressed in E. coli and was shown to be partially mono-phosphorylated, as assessed by mass spectrometry of the purified protein. Crystals of un-phosphorylated protein were obtained and diffraction data collected to 2.5 A resolution. The structure of NM-IIANtr was solved by molecular replacement using the coordinates of the E. coli nitrogen regulatory protein IIAntr [PDB: 1A6J] as the starting model. The overall fold of the Neisseria enzyme shows a high degree of similarity to the IIANtr from E. coli, and the position of the phosphoryl acceptor histidine residue (H67) is conserved. The orientation of an adjacent arginine residue (R69) suggests that it may also be involved in coordinating the phosphate group. Comparison of the structure with that of E. coli IIAmtl complexed with HPr [PDB: 1J6T] indicates that NM-IIANtr binds in a similar way to the HPr-like enzyme in Neisseria.


CONCLUSIONS
The structure of NM-IIANtr confirms its assignment as a homologue of the IIANtr proteins found in a range of other Gram-negative bacteria. We conclude that the NM- IIANtr protein functions as part of a phosphorylation cascade which, in contrast to E. coli, shares the upstream phosphotransfer protein with the sugar uptake phosphoenolpyruvate:sugar phosphotransferase system (PTS), but in common with E. coli has a distinct downstream effector mechanism.
Ren
Jingshan
J
The Oxford Protein Production Facility, Henry Wellcome Building for Genomic Medicine, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, UK. ren@strubi.ox.ac.uk
Sainsbury
Sarah
S
Berrow
Nick S
NS
Alderton
David
D
Nettleship
Joanne E
JE
Stammers
David K
DK
Saunders
Nigel J
NJ
Owens
Raymond J
RJ
D001120:Arginine / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry*; D001483:Base Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D017931:DNA Primers / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D006090:Gram-Negative Bacteria / Q000378:metabolism; D006639:Histidine / Q000737:chemistry; D013058:Mass Spectrometry; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D009345:Neisseria meningitidis / Q000378:metabolism*; D009584:Nitrogen / Q000737:chemistry*; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000737:chemistry*; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D040901:Proteomics / Q000379:methods
D001426:Bacterial Proteins; D017931:DNA Primers; C423631:PtsN protein, Pseudomonas putida; D006639:Histidine; D001120:Arginine; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D009584:Nitrogen