Uncoupling of transfer of the presequence and unfolding of the mature domain in precursor translocation across the mitochondrial outer membrane

Takashi Kanamori, Shuh Ichi Nishikawa, Masato Nakai, Injae Shin, Peter G. Schultz, Toshiya Endo

Research output: Contribution to journalArticle

70 Citations (Scopus)

Abstract

Translocation of mitochondrial precursor proteins across the mitochondrial outer membrane is facilitated by the translocase of the outer membrane (TOM) complex. By using site-specific photocrosslinking, we have mapped interactions between TOM proteins and a mitochondrial precursor protein arrested at two distinct stages, stage A (accumulated at 0°C) and stage B (accumulated at 30°C), in the translocation across the outer membrane at high resolution not achieved previously. Although the stage A and stage B intermediates were assigned previously to the forms bound to the cis site and the trans site of the TOM complex, respectively, the results of crosslinking indicate that the presequence of the intermediates at both stage A and stage B is already on the trans side of the outer membrane. The mature domain is unfolded and bound to Tom40 at stage B whereas it remains folded at stage A. After dissociation from the TOM complex, translocation of the stage B intermediate, but not of the stage A intermediate, across the inner membrane was promoted by the intermembrane-space domain of Tom22. We propose a new model for protein translocation across the outer membrane, where translocation of the presequence and unfolding of the mature domain are not necessarily coupled.

Original languageEnglish
Pages (from-to)3634-3639
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume96
Issue number7
DOIs
Publication statusPublished - 1999 Mar 30

All Science Journal Classification (ASJC) codes

  • General

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