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The N‐terminal domain of Tob55 has a receptor‐like function in the biogenesis of mitochondrial β‐barrel proteins
Author(s) -
Habib Shukry James,
Neupert Walter,
Rapaport Doron
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a611-b
Subject(s) - barrel (horology) , intermembrane space , microbiology and biotechnology , bacterial outer membrane , biogenesis , egf like domain , mitochondrion , biology , translocase of the outer membrane , c terminus , mitochondrial intermembrane space , inner mitochondrial membrane , chemistry , mitochondrial membrane transport protein , biochemistry , binding domain , binding site , amino acid , gene , escherichia coli , composite material , materials science
β‐barrel proteins constitute a distinct class of mitochondrial outer membrane proteins. For import into mitochondria their precursor forms engage the TOM complex. They are then relayed to the TOB complex that mediates their insertion into the outer membrane. Tob55 is an essential component of the TOB complex. It is anchored to the outer membrane by a C‐terminal β‐barrel domain, while the N‐terminal domain is exposed to the intermembrane space. Therefore, precursors of β‐barrel proteins which are on their way from the TOM to the TOB complex could interact with this domain. Deletions of N‐terminal domain of Tob55 precursor did not affect the targeting of the precursor to mitochondria and its insertion into the outer membrane. Replacement of wild type Tob55 by these deletion variants resulted in reduced growth of cells. Mitochondria isolated from such cells contain reduced levels of β‐barrel proteins and are impaired in their capacity to import newly synthesized β‐barrel precursors. The purified N‐terminal domain of Tob55 is able to bind β‐barrel precursors in a specific manner. Taken together, these results demonstrate that the N‐terminal domain of Tob55 has a function in recognizing precursors of β‐barrel proteins. We propose that the receptor‐like function of the N‐terminal domain of Tob55 has a role in coupling the translocation of β‐barrel precursors across the TOM complex to their interaction with the TOB complex.

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