Adapter protein required for efficient degradation of Spx by ClpXP under non-stress conditions (By similarity). Interaction with Spx stabilizes Spx and exposes the C-terminus of Spx for recognition and proteolysis by ClpXP (PubMed:30982633). Monomer (PubMed:30982633). Interacts with Spx (PubMed:30982633). Contains a DsbA-like thioredoxin domain connected via a linker to a C-terminal domain reminiscent of the winged helix-turn-helix fold. Belongs to the SpxH family.