Send to

Choose Destination
See comment in PubMed Commons below
Mol Biol Cell. 2008 Jan;19(1):126-36. Epub 2007 Oct 31.

The peripheral membrane subunits of the SAM complex function codependently in mitochondrial outer membrane biogenesis.

Author information

Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria 3010, Australia.


The sorting and assembly machinery (SAM) complex functions in the assembly of beta-barrel proteins into the mitochondrial outer membrane. It is related to the Omp85/YaeT machinery in bacterial outer membranes, but the eukaryotic SAM complex is distinguished by two peripheral subunits, Sam37 and Sam35, that sit on the cytosolic face of the complex. The function of these subunits in beta-barrel protein assembly is currently unclear. By screening a library of sam35 mutants, we show that 13 distinct alleles were each specifically suppressed by overexpression of SAM37. Two of these mutants, sam35-409 and sam35-424, show distinct phenotypes that enable us to distinguish the function of Sam35 from that of Sam37. Sam35 is required for the SAM complex to bind outer membrane substrate proteins: destabilization of Sam35 inhibits substrate binding by Sam50. Sam37 acts later than Sam35, apparently to assist release of substrates from the SAM complex. Very different environments surround bacteria and mitochondria, and we discuss the role of Sam35 and Sam37 in terms of the problems peculiar to mitochondrial protein substrates.

[Indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Support Center