Cloning and characterization of a panel of mitochondrial targeting sequences for compartmentalization engineering in Saccharomyces cerevisiae

Mitochondrion is generally considered as the most promising subcellular organelle for compartmentalization engineering. Much progress has been made in reconstituting whole metabolic pathways in the mitochondria of yeast to harness the precursor pools (i.e., pyruvate and acetyl-CoA), bypass competing pathways, and minimize transportation limitations. However, only a few mitochondrial targeting sequences (MTSs) have been characterized (i.e., MTS of COX4), limiting the application of compartmentalization engineering for multigene biosynthetic pathways in the mitochondria of yeast. In the present study, based on the mitochondrial proteome, a total of 20 MTSs were cloned and the efficiency of these MTSs in targeting heterologous proteins, including the Escherichia coli FabI and enhanced green fluorescence protein (EGFP) into the mitochondria was evaluated by growth complementation and confocal microscopy. After systematic characterization, six of the well-performed MTSs were chosen for the colocalization of complete biosynthetic pathways into the mitochondria. As proof of concept, the full alpha-santalene biosynthetic pathway consisting of 10 expression cassettes capable of converting acetyl-coA to alpha-santalene was compartmentalized into the mitochondria, leading to a 3.7-fold improvement in the production of alpha-santalene. The newly characterized MTSs should contribute to the expanded metabolic engineering and synthetic biology toolbox for yeast mitochondrial compartmentalization engineering.

Automated summary

The study cloned 20 mitochondrial targeting sequences (MTSs) based on the mitochondrial proteome, and evaluated their efficiency in targeting heterologous proteins to the mitochondria. After systematic characterization, six well-performed MTSs were chosen for colocalization of complete biosynthetic pathways into the mitochondria.