A protein interaction map of the myosin Myo2 reveals a role of Alo1 in mitochondrial inheritance in yeast.

Budding yeast cells multiply by asymmetric cell division. During this process, the cell organelles are transported by myosin motors along the actin cytoskeleton into the growing bud, while at the same time some organelles must be retained in the mother cell. The ordered partitioning of organelles depends on highly regulated binding of motor proteins to cargo membranes. To search for novel components involved in this process, we performed a protein fragment complementation screen using the cargo binding domain of Myo2, the major organelle transporter in yeast, as a bait and a genome-wide strain collection expressing yeast proteins as prey. One robust hit was Alo1, a poorly characterized D-arabinono-1,4-lactone oxidase located in the mitochondrial outer membrane. We found that mutants lacking Alo1 exhibit defects in mitochondrial morphology and inheritance. During oxidative stress dysfunctional mitochondria are immobilized in the mother in wild type cells. Intriguingly, overexpression of ALO1 restores bud-directed transport of mitochondria under these conditions. We propose that Alo1 supports the recruitment of Myo2 to mitochondria and its activity is particularly important under oxidative stress.