Functional staging of ADP/ATP carrier translocation across the outer mitochondrial membrane
The ADP/ATP carrier (AAC) is the major representative of the inner membrane carrier proteins of mitochondria that are synthesized without cleavable presequences. The characterization of the import pathway of AAC into mitochondria has mainly depended on an operational staging system. Here, we introdu...
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Published in | The Journal of biological chemistry Vol. 274; no. 29; pp. 20619 - 20627 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
United States
American Society for Biochemistry and Molecular Biology
16.07.1999
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Subjects | |
Online Access | Get full text |
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Summary: | The ADP/ATP carrier (AAC) is the major representative of the inner membrane carrier proteins of mitochondria that are synthesized
without cleavable presequences. The characterization of the import pathway of AAC into mitochondria has mainly depended on
an operational staging system. Here, we introduce two approaches for analyzing the import of AAC, blue native electrophoresis
and folding-induced translocation arrest, that allow a functional staging of AAC transport across the outer membrane. (i)
Blue native electrophoresis permits a direct monitoring of the receptor stage of AAC and its chase into mitochondria. Binding
to this stage requires the receptor protein Tom70 but not Tom37 or Tom20. (ii) A fusion protein between AAC and dihydrofolate
reductase can be selectively arrested in the general import pore complex of the outer membrane by ligand induced folding of
the passenger protein. Cross-linking demonstrates that the arrested preprotein is in close contact not only with several receptors
and Tim10 but also with the channel protein Tom40, providing the first direct evidence that cleavable preproteins and carrier
preproteins interact with the same outer membrane channel. The staging system presented here permits a molecular dissection
of AAC transport across the outer mitochondrial membrane, relates it to functional units of the translocases, and indicates
a coordinated and successive cooperation of distinct translocase subcomplexes during transfer of the preprotein. |
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Bibliography: | http://www.jbc.org/ ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.274.29.20619 |