TY - JOUR
T1 - The Tom40 assembly process probed using the attachment of different intramitochondrial sorting signals
AU - Shiota, Takuya
AU - Maruyama, Miyuki
AU - Miura, Mami
AU - Tamura, Yasushi
AU - Yamano, Koji
AU - Esaki, Masatoshi
AU - Endo, Toshiya
PY - 2012/10/15
Y1 - 2012/10/15
N2 - The TOM40 complex is a protein translocator in the mitochondrial outer membrane and consists of several different subunits. Among them, Tom40 is a central subunit that constitutes a protein-conducting channel by forming a β-barrel structure. To probe the nature of the assembly process of Tom40 in the outer membrane, we attached various mitochondrial presequences to Tom40 that possess sorting information for the intermembrane space (IMS), inner membrane, and matrix and would compete with the inherent Tom40 assembly process. We analyzed the mitochondrial import of those fusion proteins in vitro. Tom40 crossed the outer membrane and/or inner membrane even in the presence of various sorting signals. N-terminal anchorage of the attached presequence to the inner membrane did not prevent Tom40 from associating with the TOB/SAM complex, although it impaired its efficient release from the TOB complex in vitro but not in vivo. The IMS or matrix-targeting presequence attached to Tom40 was effective in substituting for the requirement for small Tim proteins in the IMS for the translocation of Tom40 across the outer membrane. These results provide insight into the mechanism responsible for the precise delivery of β-barrel proteins to the outer mitochondrial membrane.
AB - The TOM40 complex is a protein translocator in the mitochondrial outer membrane and consists of several different subunits. Among them, Tom40 is a central subunit that constitutes a protein-conducting channel by forming a β-barrel structure. To probe the nature of the assembly process of Tom40 in the outer membrane, we attached various mitochondrial presequences to Tom40 that possess sorting information for the intermembrane space (IMS), inner membrane, and matrix and would compete with the inherent Tom40 assembly process. We analyzed the mitochondrial import of those fusion proteins in vitro. Tom40 crossed the outer membrane and/or inner membrane even in the presence of various sorting signals. N-terminal anchorage of the attached presequence to the inner membrane did not prevent Tom40 from associating with the TOB/SAM complex, although it impaired its efficient release from the TOB complex in vitro but not in vivo. The IMS or matrix-targeting presequence attached to Tom40 was effective in substituting for the requirement for small Tim proteins in the IMS for the translocation of Tom40 across the outer membrane. These results provide insight into the mechanism responsible for the precise delivery of β-barrel proteins to the outer mitochondrial membrane.
UR - http://www.scopus.com/inward/record.url?scp=84867437057&partnerID=8YFLogxK
U2 - 10.1091/mbc.E12-03-0202
DO - 10.1091/mbc.E12-03-0202
M3 - Article
C2 - 22933571
AN - SCOPUS:84867437057
SN - 1059-1524
VL - 23
SP - 3936
EP - 3947
JO - Molecular Biology of the Cell
JF - Molecular Biology of the Cell
IS - 20
ER -