The X-ray Structure of the N-terminal Domain of PILB from Neisseria meningitidis Reveals a Thioredoxin-fold

The secreted form of the PilB protein was recently shown to be bound to the outer membrane of Neisseria gonorrhoeae and proposed to be involved in survival of the pathogen to the hostʹs oxidative burst. PilB is composed of three domains. The central and the C-terminal domains display methionine sulfoxide reductase (Msr) A and B activities respectively, i.e. the ability to reduce specifically the S and the R enantiomers of the sulfoxide function of the methionine sulfoxides, which are easily formed upon oxidation of methionine residues. The N-terminal domain of PilB (Dom1PILB) of N. meningitidis, which possesses a CXXC motif, was recently shown to recycle the oxidized forms of the PilB Msr domains in vitro, as the Escherichia coli thioredoxin (Trx) 1 does.