A novel N-terminal extension in mitochondrial TRAP1 serves as a thermal regulator of chaperone activity

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Abstract

Hsp90 is a conserved chaperone that facilitates protein homeostasis. Our crystal structure of the mitochondrial Hsp90, TRAP1, revealed an extension of the N-terminal β-strand previously shown to cross between protomers in the closed state. Here we address the regulatory function of this extension or 'strap' and demonstrate it's responsibility for an unusual temperature dependence in ATPase rates. This dependence is a consequence of a thermally-sensitive kinetic barrier between the apo 'open' and ATP-bound 'closed' conformations. The strap stabilizes the closed state through trans-protomer interactions. Displacement of cis-protomer contacts from the apo state is rate-limiting for closure and ATP hydrolysis. Strap release is coupled to rotation of the N-terminal domain and dynamics of the nucleotide binding pocket lid. The strap is conserved in higher eukaryotes but absent from yeast and prokaryotes suggesting its role as a thermal and kinetic regulator, adapting Hsp90s to the demands of unique cellular and organismal environments.

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James R Partridge

Global Blood Therapeutics, San Francisco, United States

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The authors declare that no competing interests exist.
Laura A Lavery

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, United States

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The authors declare that no competing interests exist.
Daniel Elnatan

Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States

Competing interests
The authors declare that no competing interests exist.
Nariman Naber

Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States

Competing interests
The authors declare that no competing interests exist.
Roger Cooke

Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States

Competing interests
The authors declare that no competing interests exist.
David A Agard

Department of Chemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, United States

For correspondence
agard@msg.ucsf.edu

Competing interests
The authors declare that no competing interests exist.

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