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PMID: 18039934 Published · ppublish English Journal Article Research Support, Non-U.S. Gov't

Alternative function for the mitochondrial SAM complex in biogenesis of alpha-helical TOM proteins.

The Journal of cell biology ·Vol. 179 ·No. 5 ·2007-12-03 ·Pages 881-93

Stojanovski D, Guiard B, Kozjak-Pavlovic V, Pfanner N, Meisinger C

Abstract

The mitochondrial outer membrane contains two preprotein translocases: the general translocase of outer membrane (TOM) and the beta-barrel-specific sorting and assembly machinery (SAM). TOM functions as the central entry gate for nuclear-encoded proteins. The channel-forming Tom40 is a beta-barrel protein, whereas all Tom receptors and small Tom proteins are membrane anchored by a transmembrane alpha-helical segment in their N- or C-terminal portion. Synthesis of Tom precursors takes place in the cytosol, and their import occurs via preexisting TOM complexes. The precursor of Tom40 is then transferred to SAM for membrane insertion and assembly. Unexpectedly, we find that the biogenesis of alpha-helical Tom proteins with a membrane anchor in the C-terminal portion is SAM dependent. Each SAM protein is necessary for efficient membrane integration of the receptor Tom22, whereas assembly of the small Tom proteins depends on Sam37. Thus, the substrate specificity of SAM is not restricted to beta-barrel proteins but also includes the majority of alpha-helical Tom proteins.

MeSH Terms
Membrane Transport Proteins/metabolism Mitochondria/metabolism Mitochondrial Membrane Transport Proteins Mitochondrial Membranes/metabolism Mitochondrial Proteins/metabolism Mitochondrial Swelling Multiprotein Complexes/metabolism Mutation/genetics Protein Precursors/metabolism Protein Structure, Secondary Protein Subunits/metabolism Saccharomyces cerevisiae/cytology,metabolism Saccharomyces cerevisiae Proteins/chemistry,metabolism
Chemicals
Membrane Transport Proteins Mitochondrial Membrane Transport Proteins Mitochondrial Proteins Multiprotein Complexes Protein Precursors Protein Subunits Saccharomyces cerevisiae Proteins Sam35 protein, S cerevisiae TOM22 protein, S cerevisiae
Authors & Affiliations
5 authors, click to expand affiliations / ORCID
Stojanovski Diana
Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Universität Freiburg, D-79104 Freiburg, Germany.
Guiard Bernard
Kozjak-Pavlovic Vera
Pfanner Nikolaus
Meisinger Chris
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Article Info
Journal
The Journal of cell biology
Abbr.
J Cell Biol
ISSN
1540-8140
DOI
10.1083/jcb.200706043
Published
2007-12-03
Epub
2007-00-26
Pages
881-93
Language
English
Region
United States
NLM ID
0375356
PMCID
PMC2099199
Subset
IM
Corrections
ErratumIn
-
External Links
PubMed source DOI: 10.1083/jcb.200706043 PMC Full Text View journal details
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