Targeting to mitochondria brings a protein to a completely different subcellular environment capable of different metabolic and catabolic functions. The ImpactVector1.5 vector uses the yeast CoxIV secretion signal which was shown to deliver proteins in the mitochondrial matrix. The protein is fused to the first 4 amino acids of the yeast CoxIV protein in order to allow proper processing of the signal peptide (Kohler et al. Plant J 11: 613-621 (1997)).