O. Kerscher et al., Tim18p is a new component of the Tim54p-Tim22p translocon in the mitochondrial inner membrane, MOL BIOL CE, 11(1), 2000, pp. 103-116
The mitochondrial inner membrane contains two separate translocons: one req
uired for the translocation of matrix-targeted proteins (the Tim23p-Tim17p
complex) and one for the insertion of polytopic proteins into the mitochond
rial inner membrane (the Tim54p-Tim22p complex). To identify new members of
the Tim54p-Tim22p complex, we screened for high-copy suppressors of the te
mperature-sensitive tim54-1 mutant. We identified a new gene, TIM18, that e
ncodes an integral protein of the inner membrane. The following genetic and
biochemical observations suggest that the Tim18 protein is part of the Tim
54p-Tim22p complex in the inner membrane: multiple copies of TIM18 suppress
the tim54-1 growth defect; the tim18::HIS3 disruption is synthetically let
hal with tim54-1; Tim54p and Tim22p can be coimmune precipitated with the T
im18 protein; and Tim18p, along with Tim54p and Tim22p, is detected in an s
imilar to 300-kDa complex after blue native electrophoresis. We propose tha
t Tim18p is a new component of the Tim54p-Tim22p machinery that facilitates
insertion of polytopic proteins into the mitochondrial inner membrane.