New molecular interaction of IIA^Ntr and HPr from Burkholderia pseudomallei identified by X‐ray crystallography and docking studies

Abstract

The nitrogen-related phosphoenolpyruvate phosphotransferase system (PTS(Ntr) ) is involved in controlling ammonia assimilation and nitrogen fixation. The additional role of PTS(Ntr) as a regulatory link between nitrogen and carbon utilization in Escherichia coli is assumed to be closely related to molecular functions of IIA(Ntr) in potassium homeostasis. We have determined the crystal structure of IIA(Ntr) from Burkholderia pseudomallei (BpIIA(Ntr) ), which is a causative agent of melioidosis. The crystal structure of dimeric BpIIA(Ntr) determined at 3.0 Å revealed that its active sites are mutually blocked. This dimeric state is stabilized by charge and weak hydrophobic interactions. Overall monomeric structure and the active site residues, Arg51 and His67, of BpIIA(Ntr) are well conserved with those of IIA(Ntr) enzymes from E. coli and Neisseria meningitides. Interestingly, His113 of BpIIA(Ntr) , which corresponds to a key residue in another phosphoryl group relay in the mannitol-specific enzyme EIIA family (EIIA(Mtl) ), is located away from the active site due to the loop connecting β5 and α3. Combined with other differences in molecular surface properties, these structural signatures distinguish the IIA(Ntr) family from the EIIA(Mtl) family. Since, there is no gene for NPr in the chromosome of B. pseudomallei, modeling and docking studies of the BpIIA(Ntr) -BpHPr complex has been performed to support the proposal on the NPr-like activity of BpHPr. A potential dual role of BpHPr as a nonspecific phosphocarrier protein interacting with both sugar EIIAs and IIA(Ntr) in B. pseudomallei has been discussed.

Phosphotransferase protein EIIANtr interacts with SpoT, a key enzyme of the stringent response, in Ralstonia eutropha H16

“…Generally, the phosphorylated form of EIIA Ntr prevails when cells grow in rich media (Bahr et al, 2011;Jahn et al, 2013;Pflüger & de Lorenzo, 2007). In contrast to the canonical EI, EI Ntr contains a GAF signalling domain, which modulates autophosphorylation of EI Ntr and thereby the phosphorylation state of PTS Ntr (Lee et al, 2013).…”

“…Similar to other b-Proteobacteria, R. eutropha contains EIIA Ntr but lacks EI Ntr and NPr (Pflüger-Grau & Görke, 2010). In contrast, canonical HPr and EI proteins serve to phosphorylate EIIA Ntr and EIIA Man , which is another EIIA-like protein (Kim et al, 2013;Krauße et al, 2009). R. eutropha also possesses HPr kinase/phosphorylase (HPrK/P), which phosphorylates HPr at Ser46 ( Fig.…”