A proteomic analysis of the regulon of the NarP two-component regulatory system response regulator in the bovine pathogen Mannheimia haemolytica A1

Background The response of the NarQP two-component signal transduction system regulon in response to the presence of nitrate for the bovine pathogen Mannheimia haemolytica A1 was investigated by proteomic analysis. Total proteins from a narP mutant and the parent SH1217 grown with or without NaNO 3 supplement were examined by ISO-DALT 2D electrophoresis and liquid chromatography-mass spectrometry. Results Seventeen proteins were differentially expressed in the parent strain SH1217 in response to the addition of NaNO 3 to the growth media. These responses were absent in the narP mutant, indicating that the altered production of these proteins is mediated by NarP Mh . Interestingly, NarP Mh mediated the increased production of some proteins which are not generally associated with nitrate respiration, such as the iron transporters FbpA and YfeA. The increased production of proteins such as superoxide dismutase, SodA, and GAPDH were also observed. The increased production of these iron-regulated proteins by NarP Mh is thought to enhance the swift establishment of the nitrate respiration mechanism of M. haemolytica during pathogenesis. Conclusion The data suggested NarP Mh acts as an important regulator which regulates the expression of a small set of proteins in response to nitrate availability. This may contribute to the prevalence of M. haemolytica A1 in its host during pathogenesis of BPP, through enhancing the effectiveness of nitrate respiration either directly or indirectly.