The protease adaptor YjbH is involved in the nitrosative stress response in Listeria monocytogenes and requires its thioredoxin active motif for function

Abstract

Tight regulation of virulence proteins is essential for the facultative intracellular pathogen Listeria monocytogenes to successfully infect host cells. The gene encoding the annotated thioredoxin YjbH was identified in two forward genetic screens as required for virulence factor production. However, the function of YjbH in L. monocytogenes has not been investigated. This dissertation provides evidence that L. monocytogenes YjbH is a protease adaptor for the redox-responsive transcriptional regulator SpxA1, and is involved in the nitrosative stress response. Whole-cell proteomics demonstrated that YjbH alters the abundance of at least 8 proteins in addition to SpxA1, and we showed that YjbH physically interacted with all 9 in bacterial two-hybrid assays. Thioredoxin proteins canonically require active motif cysteines for function, but other YjbH homologues do not. We demonstrated that cysteine residues of the YjbH thioredoxin domain active motif are essential for L. monocytogenes sensitivity to nitrosative stress, cell-to-cell spread in a tissue culture model of infection, and several protein-protein interactions. Together, these results demonstrated that the function of YjbH in L. monocytogenes requires its thioredoxin active motif and that YjbH has a role in the post-translational regulation of several proteins, including SpxA1.