Dual interaction of scaffold protein Tim44 of mitochondrial import motor with channel-forming translocase subunit Tim23

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Abstract

Proteins destined for the mitochondrial matrix are targeted to the inner membrane Tim17/23 translocon by their presequences. Inward movement is driven by the matrix-localized, Hsp70-based motor. The scaffold Tim44, interacting with the matrix face of the translocon, recruits other motor subunits and binds incoming presequence. The basis of these interactions and their functional relationships remains unclear. Using site-specific in vivo crosslinking and genetic approaches in Saccharomyces cerevisiae, we found that both domains of Tim44 interact with the major matrix-exposed loop of Tim23, with the C-terminal domain (CTD) binding Tim17 as well. Results of in vitro experiments showed that the N-terminal domain (NTD) is intrinsically disordered and binds presequence near a region important for interaction with Hsp70 and Tim23. Our data suggest a model in which the CTD serves primarily to anchor Tim44 to the translocon, whereas the NTD is a dynamic arm, interacting with multiple components to drive efficient translocation.

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See-Yeun Ting

Department of Biochemistry, University of Wisconsin-Madison, Madison, United States

Competing interests
The authors declare that no competing interests exist.
Nicholas L Yan

Department of Biochemistry, University of Wisconsin-Madison, Madison, United States

Competing interests
The authors declare that no competing interests exist.
Brenda A Schilke

Department of Biochemistry, University of Wisconsin-Madison, Madison, United States

Competing interests
The authors declare that no competing interests exist.
Elizabeth A Craig

Department of Biochemistry, University of Wisconsin-Madison, Madison, United States

For correspondence
ecraig@wisc.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-9381-4307

Funding

National Institutes of Health (GM27870)

See-Yeun Ting
Nicholas L Yan
Brenda A Schilke
Elizabeth A Craig

Department of Biochemistry, University of Wisconsin-Madison (Steenbock Predoctoral Fellowship)

See-Yeun Ting

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.