The protein-protein interaction network of the Escherichia coli EIIA Ntr regulatory protein reveals a role in cell motility and metabolic control.

The nitrogen-related PTS ^Ntr system, present in many Proteobacteria including Escherichia coli, acts as a phosphorelay cascade composed of the EI ^Ntr , NPr and EIIA ^Ntr proteins. Phosphotransfer initiates with phosphoenolpyruvate-dependent EI ^Ntr autophosphorylation, the phosphoryl group is then transferred to NPr and finally to a conserved histidine residue on EIIA ^Ntr . The reporter metabolites l-glutamine and 2-oxoglutarate reciprocally regulate EI ^Ntr autophosphorylation (Lee et al., 2013) and consequently the phosphorylation status of the PTS ^Ntr components is controlled by the availability of nitrogen and carbon. The final phosphate acceptor, EIIA ^Ntr , regulates a range of cellular process by acting as the central hub of a complex protein-protein interaction network. Contact between EIIA ^Ntr and its target proteins is usually regulated by the EIIA ^Ntr phosphorylation status. In this study we performed ligand fishing assays coupled to label-free quantitative proteomics to examine the protein-protein interaction network of E. coli EIIA ^Ntr and a phosphomimic variant of the protein. The ligand fishing data, along with phenotypic analysis, indicated that EIIA ^Ntr interacts with proteins related to chemotaxis and thereby regulates cell motility. Important metabolic enzymes were also identified as potential EIIA ^Ntr binding partners.
Competing Interests: Declaration of competing interest Authors have no conflict of interest to declare.
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