Part of the pafABC operon, however PafB does not seem to be involved in pupylation or substrate degradation. Appears to play at least a small role in resistance to reactive nitrogen intermediates (RNI) in vitro. Interacts with PafC; with which it probably forms a heterocomplex. Cells lacking this gene are not severely sensitized to RNI and display no accumulation of the proteasome substrates mpa, FabD and PanB. Belongs to the PafB family.