Regulation of chaperone function by coupled folding and oligomerization

Area of Science:

• Molecular biology
• Structural biology
• Microbiology

Background:

• The homotrimeric molecular chaperone Skp facilitates outer membrane protein transport in Gram-negative bacteria.
• The mechanism regulating Skp's functional cycle and activity modulation remains poorly understood.

Purpose of the Study:

• To characterize the atomic-resolution monomer-trimer transition of Escherichia coli Skp.
• To elucidate the folding mechanism and client protein-mediated activation of Skp.

Main Methods:

• Atomic-resolution characterization of Skp oligomerization.
• Structural analysis of Skp monomer and trimer states.
• In vivo studies assessing Skp's role in bacterial infection models.

Main Results:

• Monomeric Skp is intrinsically disordered; trimer formation involves a unique alpha-helical coiled-coil stapling mechanism.
• Client protein binding simultaneously engages all three Skp subunits, promoting the active trimeric state.
• This client-induced activation mechanism is critical for Salmonella fitness during mouse infection.

Conclusions:

• Skp activity is modulated by client protein binding through a coupled folding and activation mechanism.
• This ATP-independent mechanism represents a novel mode of chaperone regulation essential for bacterial survival and pathogenesis.