Editor: Lubomir Tomaska
Mitochondrial preprotein translocases as dynamic molecular machines
Article first published online: 17 JUL 2006
FEMS Yeast Research
Volume 6, Issue 6, pages 849–861, September 2006
How to Cite
Van Der Laan, M., Rissler, M. and Rehling, P. (2006), Mitochondrial preprotein translocases as dynamic molecular machines. FEMS Yeast Research, 6: 849–861. doi: 10.1111/j.1567-1364.2006.00134.x
- Issue published online: 17 JUL 2006
- Article first published online: 17 JUL 2006
- Received 24 March 2006; revised 9 May 2006; accepted 12 May 2006.First published online 17 July 2006.
- mitochondrial protein import;
- TIM23 complex;
- PAM complex
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.