The moonlighting peroxiredoxin-glutaredoxin in Neisseria meningitidis binds plasminogen via a C-terminal lysine residue and contributes to survival in a whole blood model

Neisseria meningitidis is a human-restricted bacterium that can invade the bloodstream and cross the blood-brain barrier resulting in life-threatening sepsis and meningitis. Meningococci express a cytoplasmic peroxiredoxin-glutaredoxin (Prx5-Grx) hybrid protein that has also been identified on the bacterial surface. Here, recombinant Prx5-Grx was confirmed as a plasminogen (Plg)-binding protein, in an interaction which could be inhibited by the lysine analogue epsilon-aminocapronic acid. rPrx5-Grx derivatives bearing a substituted C-terminal lysine residue (rprx5-Grx(K244A)), but not the active site cysteine residue (rPrx5-Gni(C185A)) or the sub-terminal rPrx5-Grx(K230A) lysine residue, exhibited significantly reduced Plg-binding. The absence of Prx5-Grx did not significantly reduce the ability of whole meningococcal cells to bind Plg, but under hydrogen peroxide-mediated oxidative stress, the N. meningitidis Delta pxn5-grx mutant survived significantly better than the wild-type or complemented strains. Significantly, using human whole blood as a model of meningococcal bacteremia, it was found that the N. meningitidis Delta pxn5-grx mutant had a survival defect compared with the parental or complemented strain, confirming an important role for Prx5-Grx in meningococcal pathogenesis.