Adapter protein required for efficient degradation of Spx by ClpXP under non-stress conditions (PubMed:22194450, PubMed:32117138). Interaction with Spx stabilizes Spx and exposes the C-terminus of Spx for recognition and proteolysis by ClpXP (By similarity). Involved in disulfide stress regulation (PubMed:21947404). In non-stressed conditions, mainly remains soluble (PubMed:32117138). Forms aggregates in response to different environmental stresses such as heat shock, oxidative stress and antibiotic treatment, and cannot assist Spx degradation (PubMed:32117138). Interacts with Spx. Inactivation of the gene increases the level of Spx protein and transcription of the Spx-regulated gene trxB (PubMed:22194450). Disruption leads to an increase in hla (alpha-hemolysin) transcription and proteases production (PubMed:16923874). It also leads to increased tolerance to the disulfide stress inducing compound diamide, increased peptidoglycan cross-linking, and moderate resistance to oxacillin and other beta-lactams antibiotics (PubMed:21947404). Goehring et al. suggest that the cysteine residues are important for the role of YjbH/SpxH in disulfide stress management (PubMed:21947404). However, mutation of all seven cysteine residues in B.subtilis ortholog by Engman et al. shows that these cysteines are dispensable for the function of the protein and that the activity of the adapter is not activated or deactivated via redox-active cysteines (PubMed:22194450). Belongs to the SpxH family.