cis and trans sites of the TOM complex of mitochondria in unfolding and initial translocation of preproteins.

The Journal of Biological Chemistry
D RapaportR Lill

Abstract

Translocation of preproteins across the mitochondrial outer membrane is mediated by the TOM complex. Our previous studies led to the concept of two preprotein binding sites acting in series, the surface-exposed cis site and the trans site exposed to the intermembrane space. We report here that preproteins are bound to the cis site in a labile fashion even at low ionic strength, whereas intermediates arrested at the trans site remained firmly bound at higher salt concentration. The stability of the trans site intermediate results from interactions of both the presequence and unfolded parts of the mature part of the preprotein with the TOM complex. Binding to the trans site proceeded at rates comparable with those of unfolding of the mature domain and appeared to be kinetically limited by the unfolding reaction. Efficient binding to the trans site and unfolding were observed with both outer membrane vesicles and intact mitochondria whose membrane potential, DeltaPsi, was dissipated. Upon re-establishing DeltaPsi, trans site-bound preprotein resumed translocation into the matrix. The rates of unfolding and binding to the trans site were the same as those for translocation into intact energized mitochondria. We conclude that prepro...Continue Reading

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Citations

Aug 20, 2009·Journal of Bioenergetics and Biomembranes·Małgorzata BudzińskaHanna Kmita
Nov 5, 1999·Biochimica Et Biophysica Acta·W VoosN Pfanner
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Apr 12, 2006·Proceedings of the National Academy of Sciences of the United States of America·Paolo De Los RiosPierre Goloubinoff
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Aug 26, 1998·Molecular and Cellular Biology·D RapaportR Lill

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