Diversity in degrees of freedom of mitochondrial transit peptides.

Most mitochondrial proteins are synthesized in the cytosol of eukaryotic cells as precursor proteins carrying N-terminal extensions called transit peptides or presequences, which mediate their specific transport into mitochondria. However, plant cells possess a second potential target organelle for such transit peptides, the chloroplast. It can therefore be assumed that mitochondrial transit peptides in plants are exposed to an increased demand of specificity, which in turn leads to reduced degrees of freedom in these transit peptides compared with those of nonplant organisms. Our study investigates this hypothesis using fractal dimension. Statistical analysis of sequence data shows that the fractal dimension of mitochondrial transit peptides in plants is indeed significantly lower than that from nonplant organisms.