Chaperones Skp and SurA dynamically expand unfolded OmpX and synergistically disassemble oligomeric aggregates

Periplasmic chaperones 17-kilodalton protein (Skp) and survival factor A (SurA) are essential players in outer membrane protein (OMP) biogenesis. They prevent unfolded OMPs from misfolding during their passage through the periplasmic space and aid in the disassembly of OMP aggregates under cellular stress conditions. However, functionally important links between interaction mecha-nisms, structural dynamics, and energetics that underpin both Skp and SurA associations with OMPs have remained largely unre-solved. Here, using single-molecule fluorescence spectroscopy, we dissect the conformational dynamics and thermodynamics of Skp and SurA binding to unfolded OmpX and explore their disaggre-gase activities. We show that both chaperones expand unfolded OmpX distinctly and induce microsecond chain reconfigurations in the client OMP structure. We further reveal that Skp and SurA bind their substrate in a fine-tuned thermodynamic process via enthalpy-entropy compensation. Finally, we observed synergistic activity of both chaperones in the disaggregation of oligomeric OmpX aggregates. Our findings provide an intimate view into the multifaceted functionalities of Skp and SurA and the fine-tuned balance between conformational flexibility and underlying ener-getics in aiding chaperone action during OMP biogenesis.

Automated summary

This study investigates the essential role of periplasmic chaperones, 17-kilodalton protein (Skp) and survival factor A (SurA), in outer membrane protein (OMP) biogenesis. The researchers use single-molecule fluorescence spectroscopy to analyze the conformational dynamics and thermodynamics of Skp and SurA binding to unfolded OmpX and study their disaggre-gase activities. The findings provide insights into the multifaceted functionalities of Skp and SurA and shed light on the balance between conformational flexibility and underlying ener-getics in aiding chaperone action during OMP biogenesis.