Conserved NO-Binding Cytochromes in Burkholderia pseudomallei and Other Pathogens

SUMMARY Burkholderia pseudomallei is a recognized bioterrorism agent by the Centers for Disease Control and the causative agent of melioidosis – an emerging disease in the United States and in other developed countries. Upon infection, B. pseudomallei persists despite rapid host immune responses including exposure to macrophage-derived nitric oxide (NO). Currently, the mechanism employed by B. pseudomallei and other pathogens to evade host-produced NO is unknow. We've identified through bioinformatic studies a widely conserved gene in B. pseudomallei and in numerous other bacterial pathogens that encodes for a unique mono-heme cytochrome. We've tentatively designated this protein cyt BP1. Proteins in this family react with N-oxides including NO; however, no member in pathogens have been characterized. We hypothesize that cyt BP1 and its homologues which are present in a large group of persistent pathogens are key defense proteins that detoxify host-produced NO. We therefore propose to characterize cyt Bp1 and eventually its orthologues in other pathogens. Findings from this proposed study could be key in elucidating the mechanism employed by persistent pathogens in NO defense, persistence, and virulence. Specifically, we aim to 1. characterize the phenotype of disruption mutants encoding for bp1orthologues in model organisms 2. characterize the catalytic function of cyt BP1 in NO conversion; and 3. determine the structure-function relationship of cyt BP1. This proposal will support the very first characterization of what is likely a NO-detoxifying protein from B. pseudomallei and other pathogens. Elucidation of cyt BP1 function could be a key first step in the mechanistic understanding of the NO-defense system, and in the development of therapeutic agents for the treatment of persistent infections.