Key result
The type V myosin Myo4p binds its cargo adapter She3p via two distinct regions and is monomeric at physiological concentrations, suggesting dimerization occurs within the cargo-translocation complex.
The study demonstrates that the type V myosin Myo4p uses two binding regions for cargo interaction and likely functions as a dimer during cargo-complex transport.
No immediate clinical implications; leaves open extension to mammalian cardiac myosin transport.
Myosin-motors are conserved from yeast to human and transport a great variety of cargoes. Most plus-end directed myosins, which constitute the vast majority of all myosin motors, form stable dimers and interact constitutively with their cargo complexes. To date, little is known about regulatory mechanisms for cargo-complex assembly. In this study, we show that the type V myosin Myo4p binds to its cargo via two distinct binding regions, the C-terminal tail and a coiled-coil domain-containing fragment. Furthermore, we find that Myo4p is strictly monomeric at physiologic concentrations. Because type V myosins are thought to require dimerization for processive movement, a mechanism must be in place to ensure that oligomeric Myo4p is incorporated into cargo-translocation complexes. Indeed, we find that artificial dimerization of the Myo4p C-terminal tail promotes stabilization of myosin-cargo complexes, suggesting that full-length Myo4p dimerizes in the cocomplex as well. We also combined the Myo4p C-terminal tail with the coiled-coil region, lever arm, and motor domain from a different myosin to form constitutively dimeric motor proteins. This heterologous motor successfully translocates its cargo in vivo, suggesting that wild-type Myo4p may also function as a dimer during cargo-complex transport.
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Heuck et al. (2007) studied this question. Myo4p fragments was evaluated on Binding affinity (Kd) and complex half-life to She3p-N. The type V myosin Myo4p binds its cargo adapter She3p via two distinct regions and is monomeric at physiological concentrations, suggesting dimerization occurs within the cargo-translocation complex.