Backbone resonance assignment of the response regulator protein PhoB_N^F20D from Escherichia coli

PhoB is a response regulator of the PhoR/PhoB two-component signal transduction system that is involved in the regulation of the phosphate (Pho) regulon of Escherichia coli. PhoB has two domains, receiver domain and effector domain. The receiver domain can be phosphorylated by its cognate histidine kinase PhoR and the phosphorylation induces conformational changes of the full length protein of PhoB that promote the DNA binding and transcription. Three-dimensional crystal structures of PhoB receiver domain (PhoB_N) have been solved under apo or BeF₃^- (a phosphoryl analog) binding forms and it has been found that PhoB_N is dimerized in both situations. However, we have found that the apo form of PhoB_N has multiple conformational changes in solution that is hard to be distinguished by using NMR spectroscopy, while the mutagenesis of F20D PhoB_N gives homogeneous dispersed signals in HSQC spectrum indicating a relatively uniform conformation. Meanwhile the F20D mutant has the same phosphorylation activity as the wild type protein. Here we report the backbone assignment of PhoB_N^F20D mutant. The chemical shift (HN, N, CO, C^α and C^β) analysis shows that the predicted regions of secondary structure are in good agreement with those observed in the crystal structure of apo PhoB_N. Therefore, the backbone chemical shifts assignment of PhoB_N^F20D mutant would be useful for studying the structure and dynamics of PhoB receiver domain and it has significance for explaining the mechanism of phosphorylation in TCSs.