Skp is a multivalent chaperone of outer-membrane proteins

Area of Science:

• Microbiology
• Biochemistry
• Structural Biology

Background:

• Gram-negative bacteria utilize the trimeric chaperone Skp to transport outer-membrane proteins (OMPs).
• Skp sequesters OMPs in a hydrophobic cage, preventing aggregation during periplasmic transport.

Purpose of the Study:

• To investigate the interaction between Escherichia coli Skp and OMPs of varying sizes.
• To elucidate the mechanism of Skp-mediated OMP sequestration.

Main Methods:

• Kinetic studies of OMP folding.
• Ion mobility spectrometry-mass spectrometry (IMS-MS).
• Computer modeling and molecular dynamics simulations.

Main Results:

• Higher Skp/OMP ratios are required for larger (16-stranded) OMPs compared to smaller (8-stranded) OMPs.
• Evidence suggests 10- to 16-stranded OMPs are encapsulated within an expanded Skp substrate cage.
• Aggregation of large OMPs involves binding of additional Skp trimers.

Conclusions:

• Skp chaperone activity involves coordinating multiple trimers to protect single OMP substrates.
• This mechanism adapts to the size and structural complexity of different OMPs.
• The findings reveal a novel mode of chaperone-mediated protein transport and protection.