Structural basis for aggregate dissolution and refolding by the Mycobacterium tuberculosis ClpB-DnaK bi-chaperone...

Area of Science:

• Molecular Biology
• Structural Biology
• Microbiology

Background:

• Mycobacterium tuberculosis (Mtb) ClpB is a crucial protein disaggregase for bacterial cell survival.
• DnaK, a protein foldase, cooperates with ClpB to couple protein disaggregation and refolding.
• The precise molecular mechanism of this Mtb ClpB-DnaK interaction remains incompletely understood.

Purpose of the Study:

• To elucidate the structural mechanism of the Mtb ClpB-DnaK bi-chaperone system.
• To understand how DnaK binding influences ClpB conformation and function.
• To propose a model for the synergistic action of protein disaggregation and refolding.

Main Methods:

• Cryo-electron microscopy (cryo-EM) analysis of the Mtb ClpB-DnaK complex.
• Utilized ATPγS and a protein substrate during analysis.
• Structural analysis of protein-protein interfaces and conformational changes.

Main Results:

• Observed three distinct ClpB conformations in the presence of DnaK.
• Identified a conserved TGIP loop critical for ClpB function.
• Determined the interface between Mtb ClpB's middle domain and DnaK's nucleotide-binding domain.
• Found DnaK binding stabilizes, but does not alter the orientation of, the ClpB middle domain.

Conclusions:

• DnaK binding stabilizes Mtb ClpB, facilitating synergistic protein disaggregation and refolding.
• The TGIP loop and the ClpB-DnaK interface are key to the bi-chaperone system's function.
• A model for the coordinated action of Mtb ClpB and DnaK in protein quality control is proposed.