Mitochondrially-encoded proteins are mostly respiratory chain components.
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The mitochondrial translation system is thus organized in a very specific way.
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Initiation involves mRNA-specific activators and bacteria-like initiation factors.
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We show that Saccharomyces cerevisiae Aim23p is a functional ortholog of bacterial IF3.
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We review the lineage specific features of mitochondrial translation initiation.
Abstract
The highly streamlined mitochondrial genome encodes almost exclusively a handful of transmembrane components of the respiratory chain complex. In order to ensure the correct assembly of the respiratory chain, the products of these genes must be produced in the correct stoichiometry and inserted into the membrane, posing a unique challenge to the mitochondrial translational system. In this review we describe the proteins orchestrating mitochondrial translation initiation: bacterial-like general initiation factors mIF2 and mIF3, as well as mitochondria-specific components – mRNA-specific translational activators and mRNA-nonspecific accessory initiation factors. We consider how the fast rate of evolution in these organelles has not only created a system that is divergent from that of its bacterial ancestors, but has led to a huge diversity in lineage specific mechanistic features of mitochondrial translation initiation among eukaryotes.
