Open AccessMitochondrial preprotein translocases as dynamic molecular machines
Author(s) -
Van Der Laan Martin,
Rissler Michael,
Rehling Peter
Publication year - 2006
Publication title -
fems yeast research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.991
H-Index - 92
eISSN - 1567-1364
pISSN - 1567-1356
DOI - 10.1111/j.1567-1364.2006.00134.x
Subject(s) - translocase of the inner membrane , intermembrane space , translocase of the outer membrane , translocase , mitochondrial carrier , biology , mitochondrial membrane transport protein , protein targeting , atp–adp translocase , mitochondrion , microbiology and biotechnology , inner membrane , inner mitochondrial membrane , mitochondrial intermembrane space , dnaja3 , biochemistry , membrane protein , bacterial outer membrane , mitochondrial dna , mitochondrial fusion , gene , membrane , chromosomal translocation , escherichia coli
Proteomic studies have demonstrated that yeast mitochondria contain roughly 1000 different proteins. Only eight of these proteins are encoded by the mitochondrial genome and are synthesized on mitochondrial ribosomes. The remaining 99% of mitochondrial precursors are encoded within the nuclear genome and after their synthesis on cytosolic ribosomes must be imported into the organelle. Targeting of these proteins to mitochondria and their import into one of the four mitochondrial subcompartments – outer membrane, intermembrane space (IMS), inner membrane and matrix – requires various membrane‐embedded protein translocases, as well as numerous chaperones and cochaperones in the aqueous compartments. During the last years, several novel protein components involved in the import and assembly of mitochondrial proteins have been identified. The picture that emerges from these exciting new findings is that of highly dynamic import machineries, rather than of regulated, but static protein complexes. In this review, we will give an overview on the recent progress in our understanding of mitochondrial protein import. We will focus on the presequence translocase of the inner mitochondrial membrane, the TIM23 complex and the presequence translocase‐associated motor, the PAM complex. These two molecular machineries mediate the multistep import of preproteins with cleavable N‐terminal signal sequences into the matrix or inner membrane of mitochondria.