The Orphan Response Regulator Rv3143 Modulates the Activity of the NADH Dehydrogenase Complex (Nuo) in Mycobacterium tuberculosis via Protein-Protein Interactions

Two-component signal transduction systems enable mycobacterial cells to quickly adapt and adequately respond to adverse environmental conditions encountered at various stages of host infection. We attempted to determine the role of the Rv3143 orphan response regulator in the physiology of Mycobacterium tuberculosis and its orthologue Msmeg_2064 in Mycobacterium smegmatis. We identified the Rv3143 protein as an interaction partner for NuoD, a member of the type I NADH dehydrogenase complex involved in oxidative phosphorylation. The mutants Delta rv3143 and Delta msmeg_2064 were engineered in M. tuberculosis and M. smegmatis cells, respectively. The Delta msmeg_2064 strain exhibited a significant reduction in growth and viability in the presence of reactive nitrogen species. The Rv3143-deficient strain was sensitive to valinomycin, which is known to reduce the electrochemical potential of the cell and overexpressed genes required for nitrate respiration. An increased level of reduction of the 2,3,5-triphenyltetrazolium chloride (TTC) electron acceptor in Delta rv3143 and Delta msmeg_2064 cells was also evident. The silencing of ndh expression using CRISPRi/dCas9 affected cell survival under limited oxygen conditions. Oxygen consumption during entry to hypoxia was most severely affected in the double-mutant Delta msmeg_2064 ndh(CRISPRi/dCas9). We propose that the regulatory protein Rv3143 is a component of the Nuo complex and modulates its activity.

Automated summary

This study investigates the role of the orphan response regulator Rv3143 in the physiology of Mycobacterium tuberculosis and Mycobacterium smegmatis. The results suggest that Rv3143 interacts with NuoD and modulates its activity. Deletion of Rv3143 and msmeg_2064 leads to increased sensitivity to reactive nitrogen species and valinomycin, as well as increased reduction of the electron acceptor TTC. Silencing of ndh expression affects cell survival under limited oxygen conditions.