title: Skp is a multivalent chaperone of outer-membrane proteins.
abstract: The trimeric chaperone Skp sequesters outer-membrane proteins (OMPs) within a hydrophobic cage, thereby preventing their aggregation during transport across the periplasm in Gram-negative bacteria. Here, we studied the interaction between Escherichia coli Skp and five OMPs of varying size. Investigations of the kinetics of OMP folding revealed that higher Skp/OMP ratios are required to prevent the folding of 16-stranded OMPs compared with their 8-stranded counterparts. Ion mobility spectrometry-mass spectrometry (IMS-MS) data, computer modeling and molecular dynamics simulations provided evidence that 10- to 16-stranded OMPs are encapsulated within an expanded Skp substrate cage. For OMPs that cannot be fully accommodated in the expanded cavity, sequestration is achieved by binding of an additional Skp trimer. The results suggest a new mechanism for Skp chaperone activity involving the coordination of multiple copies of Skp in protecting a single substrate from aggregation.
authors.affiliation: Astbury Centre for Structural Molecular Biology.|School of Molecular and Cellular Biology, University of Leeds, Leeds, UK.
authors.forename: Bob
authors.initials: B
authors.lastname: Schiffrin
authors.affiliation: Astbury Centre for Structural Molecular Biology.|School of Molecular and Cellular Biology, University of Leeds, Leeds, UK.
authors.forename: Antonio N
authors.initials: AN
authors.lastname: Calabrese
authors.affiliation: Astbury Centre for Structural Molecular Biology.|School of Molecular and Cellular Biology, University of Leeds, Leeds, UK.
authors.forename: Paul W A
authors.initials: PWA
authors.lastname: Devine
authors.affiliation: Astbury Centre for Structural Molecular Biology.|School of Physics and Astronomy, University of Leeds, Leeds, UK.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Harris
authors.affiliation: Astbury Centre for Structural Molecular Biology.|School of Molecular and Cellular Biology, University of Leeds, Leeds, UK.
authors.forename: Alison E
authors.initials: AE
authors.lastname: Ashcroft
authors.affiliation: Astbury Centre for Structural Molecular Biology.|School of Molecular and Cellular Biology, University of Leeds, Leeds, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Brockwell
authors.affiliation: Astbury Centre for Structural Molecular Biology.|School of Molecular and Cellular Biology, University of Leeds, Leeds, UK.
authors.forename: Sheena E
authors.initials: SE
authors.lastname: Radford
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000502:physiology; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000502:physiology; D007700:Kinetics; D018832:Molecular Chaperones / Q000737:chemistry* / Q000502:physiology; D056004:Molecular Dynamics Simulation; D011485:Protein Binding; D000072757:Protein Conformation, beta-Strand; D017510:Protein Folding; D054730:Protein Interaction Domains and Motifs; D020836:Protein Structure, Quaternary
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; C072721:Skp protein, E coli