The terminal tail region of a yeast myosin-V mediates its attachment to vacuole membranes and sites of polarized growth

The Saccharomyces cerevisiae myosin-V, Myo2p, has been implicated in the po larized movement of several organelles and is essential for yeast viability . We have shown previously that Myo2p is required for the movement of a por tion of the lysosome (vacuole) into the bud and consequently for proper inh eritance of this organelle during cell division. Class V myosins have a glo bular carboxyl terminal tail domain that is proposed to mediate localizatio n of the myosin, possibly through interaction with organelle-specific recep tors. Here we describe a myo2 allele whose phenotypes support this hypothes is. vac15-1/myo2-2 has a single mutation in this globular tail domain, caus ing defects in vacuole movement and inheritance. Although a portion of wild -type Myo2p fractionates with the vacuole, the myo2-2 gene product does not . In addition, the mutant protein does not concentrate at sites of active g rowth, the predominant location of wild-type Myo2p. Although deletion of th e tail domain is lethal, the myo2-2 gene product retains the essential func tions of Myo2p. Moreover, myo2-2 does not cause the growth defects and leth al genetic interactions seen in mgo2-66, a mutant defective in the actin-bi nding domain. These observations suggest that the myo2-2 mutation specifica lly disrupts interactions with selected myosin receptors, namely those on t he vacuole membrane and those at sites of polarized growth.