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  • The EMBO Journal (2002) 21, 6377 - 6386
  • doi:10.1093/emboj/cdf640

Structure of eukaryotic prefoldin and of its complexes with unfolded actin and the cytosolic chaperonin CCT

Jaime Martín-Benito1,3, Jasminka Boskovic1,3, Paulino Gómez-Puertas1, José L. Carrascosa1, C.Torrey Simons2, Sally A. Lewis2, Francesca Bartolini2, Nicholas J. Cowan2 and José M. Valpuesta1

  1. Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain
  2. Department of Biochemistry, NYU Medical Center, New York, NY 10016, USA
  3. J.Martín-Benito and J.Boskovic contributed equally to this work

Correspondence to:

José M. Valpuesta, E-mail: jmv@cnb.uam.es

Received 5 June 2002; Accepted 10 October 2002; Revised 18 September 2002

The biogenesis of the cytoskeletal proteins actin and tubulin involves interaction of nascent chains of each of the two proteins with the oligomeric protein prefoldin (PFD) and their subsequent transfer to the cytosolic chaperonin CCT (chaperonin containing TCP-1). Here we show by electron microscopy that eukaryotic PFD, which has a similar structure to its archaeal counterpart, interacts with unfolded actin along the tips of its projecting arms. In its PFD-bound state, actin seems to acquire a conformation similar to that adopted when it is bound to CCT. Three-dimensional reconstruction of the CCT:PFD complex based on cryoelectron microscopy reveals that PFD binds to each of the CCT rings in a unique conformation through two specific CCT subunits that are placed in a 1,4 arrangement. This defines the phasing of the CCT rings and suggests a handoff mechanism for PFD.

  • Keywords:

    • actin,
    • chaperonin,
    • electron microscopy,
    • prefoldin,
    • protein folding