Figure 2.

Proposed model for sorting nuclear-encoded proteins to mitochondria in Arabidopsis.

A given targeting signal directs nuclear-encoded precursor proteins to mitochondria. It is proposed that to obtain targeting specificity, the targeting of chloroplast precursor proteins to mitochondria must be prevented. Current experimental data exists to explain how this might be achieved at a variety of levels, including the involvement of the mature protein, synthesis of mitochondrial proteins at the mitochondrial surface via mRNA targeting, and additional factors such as the unique composition of organellar surface receptors and lipids, development, diurnal rhythm and environmental conditions.