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

Nature Structural & Molecular Biology volume 11, pages 1015–1020 (2004)Cite this article

Abstract

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 Å. Three hairpin-shaped α-helical extensions reach out by ∼60 Å from a trimerization domain, which is composed of three intersubunit β-sheets that wind around a central axis. The α-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 Skp3–Omp complex protects the outer membrane protein from aggregation during passage through the bacterial periplasm.

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Figure 1: Molecular structure of Skp.
Figure 2: Electrostatic surface representation of Skp.
Figure 3: Hydrophobic-polar surface representations of Skp and Pfd.
Figure 4: Structural variability pattern of Skp.

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Acknowledgements

We thank J. Danzer for help with the preparation and crystallization of Skp, G. Reil for mass spectrometric analysis of SeMet derivatives, and the European Molecular Biology Laboratory Grenoble Outstation, in particular M. Walsh, for supporting measurements at the European Synchrotron Radiation Facility under the European Union Improving Human Potential Programme. This work was supported by the Fonds der Chemischen Industrie.

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  1. Lehrstuhl für Biologische Chemie, Technische Universität München, Freising-Weihenstephan, 85350, Germany

    Ingo P Korndörfer, Monica K Dommel & Arne Skerra

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Correspondence to Arne Skerra.

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Supplementary information

Supplementary Figure 1

Representative 2Fo − Fc electron density from the prong of chain C contoured at 1.0 σ. (PDF 114 kb)

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Korndörfer, I., Dommel, M. & Skerra, A. Structure of the periplasmic chaperone Skp suggests functional similarity with cytosolic chaperones despite differing architecture. Nat Struct Mol Biol 11, 1015–1020 (2004). https://doi.org/10.1038/nsmb828

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