DnaK unmasked: Potential contributions of intrinsic disorder to the hijacking of human proteostasis by a bacterial chaperone.

Bacteria are abundantly present through the body, and the proteins they secrete into the cellular microenvironment both interact with surface receptors and are internalized and interact with internal proteins responsible for important pathways and functions. One of these proteins is DnaK, a moonlighting bacterial chaperone interacting with many human proteins. Intrinsically disordered regions (IDRs) enable structural flexibility essential for multifunctionality, yet their role in DnaK and its interactors remains unclear. Analyzing data from our previous studies of Mycoplasma DnaK and human protein interactions, this study is the first to employ computational analysis to assess disorder in bacterial DnaK, bacterial proteomes, and human interactors, aiming to elucidate novel disorder-mediated mechanisms of bacterial pathogenesis. Results indicate that bacterial chaperones, including DnaK, are expected to be significantly more disordered than the proteome averages (∼27-42% chaperones are highly disordered vs. ∼7-10% proteome-wide highly disordered proteins). Human proteins interacting with bacterial DnaK cluster in chromatin organization and RNA processing networks. DnaK interactors are significantly more disordered than human HSP70/HSC70 interactors, as well as average human proteins, nuclear proteins, and proteins involved in RNA processing and DNA repair. Confirmed interactors, such as XRCC1 and USP10, feature long IDRs with many PTMs, have multiple disorder-based binding regions, and show high LLPS propensity, suggesting that disorder facilitates cellular pathways subversion. These findings are consistent with a model, in which DnaK, by virtue of its structural flexibility, may preferentially engage disordered host proteins, potentially influencing cellular pathways, paving the way for a hypothesis that warrants direct experimental validation.