A filamentous molecular chaperone of the prefoldin family from the deep-sea hyperthermophile Methanocaldococcus jannaschii

Authors

  • Timothy A. Whitehead,

    1. Department of Chemical Engineering, University of California, Berkeley, Berkeley, California 94720, USA
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  • Boonchai B. Boonyaratanakornkit,

    1. Department of Chemical Engineering, University of California, Berkeley, Berkeley, California 94720, USA
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  • Volker Höllrigl,

    1. Department of Chemical Engineering, University of California, Berkeley, Berkeley, California 94720, USA
    Current affiliation:
    1. Department of Chemical Biotechnology, University of Dortmund, 44139 Dortmund, Germany.
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  • Douglas S. Clark

    Corresponding author
    1. Department of Chemical Engineering, University of California, Berkeley, Berkeley, California 94720, USA
    Current affiliation:
    1. Department of Chemical Biotechnology, University of Dortmund, 44139 Dortmund, Germany.
    • 201 Gilman Hall, Department of Chemical Engineering, University of California, Berkeley, Berkeley, CA 94720, USA; fax: (510) 643-1228.
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Abstract

Prefoldin is a molecular chaperone found in the domains eukarya and archaea that acts in conjunction with Group II chaperonin to correctly fold other nascent proteins. Previously, our group identified a putative single subunit of prefoldin, γ PFD, that was up-regulated in response to heat stress in the hyperthermophilic archaeon Methanocaldococcus jannaschii. In order to characterize this protein, we subcloned and expressed it and the other two prefoldin subunits from M. jannaschii, α and β PFD, into Eschericia coli and characterized the proteins. Whereas α and β PFD readily assembled into the expected hexamer, γ PFD would not assemble with either protein. Instead, γ PFD forms long filaments of defined dimensions measuring 8.5 nm × 1.7–3.5 nm and lengths exceeding 1 μm. Filamentous γ PFD acts as a molecular chaperone through in vitro assays, in a manner comparable to PFD. A possible molecular model for filament assembly is discussed.

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