Structure of the periplasmic chaperone Skp suggests functional similarity with cytosolic chaperones despite differing architecture

Nat Struct Mol Biol. 2004 Oct;11(10):1015-20. doi: 10.1038/nsmb828. Epub 2004 Sep 12.


The 17-kDa protein (Skp) of Escherichia coli is a homotrimeric periplasmic chaperone for newly synthesized outer-membrane proteins. Here we present its X-ray structure at a resolution of 2.35 A. Three hairpin-shaped alpha-helical extensions reach out by approximately 60 A from a trimerization domain, which is composed of three intersubunit beta-sheets that wind around a central axis. The alpha-helical extensions approach each other at their distal turns, resulting in a fold that resembles a 'three-pronged grasping forceps'. The overall shape of Skp is reminiscent of the cytosolic chaperone prefoldin, although it is based on a radically different topology. The peculiar architecture, with apparent plasticity of the prongs and distinct electrostatic and hydrophobic surface properties, supports the recently proposed biochemical mechanism of this chaperone: formation of a Skp(3)-Omp complex protects the outer membrane protein from aggregation during passage through the bacterial periplasm.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / physiology*
  • Escherichia coli Proteins / chemistry
  • Escherichia coli Proteins / physiology*
  • Models, Molecular
  • Molecular Chaperones / chemistry
  • Molecular Chaperones / physiology*
  • Molecular Sequence Data
  • Periplasm / metabolism*
  • Protein Structure, Quaternary
  • Sequence Homology, Amino Acid
  • Surface Properties


  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • Molecular Chaperones
  • Skp protein, E coli

Associated data

  • PDB/1SG2