Mitochondrial tRNA Import and Its
Consequences for Mitochondrial Translation
Annual Review of Biochemistry
Vol. 80: 1033-1053 (Volume publication date July 2011)
First published online as a Review in Advance on March 17, 2011
DOI: 10.1146/annurev-biochem-060109-092838
André Schneider
Department of Chemistry and Biochemistry, University of Bern,
CH-3012 Bern, Switzerland; email: andre.schneider@ibc.unibe.ch
ABSTRACT
The mitochondrial genomes of most eukaryotes lack a variable
number of tRNA genes. This lack is compensated for by
import of a small fraction of the corresponding cytosolic tRNAs.
There are two broad mechanisms for the import of tRNAs into
mitochondria. In the first one, the tRNA is coimported
together with a mitochondrial precursor protein along the protein
import pathway. It applies to the yeast tRNALys and has been
elucidated in great detail. In the second more vaguely defined
mechanism, which is mainly found in plants and protozoa, tRNAs are
directly imported independent of cytosolic factors. However, results
in plants indicate that direct import of tRNAs may nevertheless
require some components of the protein import machinery. All
imported tRNAs in all systems are of the eukaryotic type but need to
be functionally integrated into the mitochondrial translation system
of bacterial descent. For some tRNAs, this is not trivial and
requires unique evolutionary adaptations.