PerspectiveCell Biology

One, two, three, cytoplasmic dynein is go!

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Science  18 Jul 2014:
Vol. 345, Issue 6194, pp. 271-272
DOI: 10.1126/science.1257245

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Molecular motors are protein machines that power the movement of many different cargoes along filamentous tracks within eukaryotic cells. The dyneins move along microtubules, with the axonemal branch of the protein family working in large teams to drive the familiar beating of cilia and flagella by causing sliding of microtubules against each other. The cytoplasmic dyneins, on the other hand, move cargoes—including chromosomes, membrane-bounded organelles, mRNA particles, and protein complexes—along single microtubules (1). An important difference between cytoplasmic dynein 1 and axonemal dyneins is that as few as one to five molecules of cytoplasmic dynein 1 are enough to move small cargoes, whereas axonemal dyneins always work together. Another distinction is that cytoplasmic dynein 1 needs the help of an additional complex—dynactin—to function in the cell (2). Exactly what dynactin does, however, has been controversial. Two new papers, McKenney et al. on page 337 of this issue (3) and Schlager et al. (4), identify a missing piece of the puzzle—specific adaptor proteins—that helps explain how dynactin and cytoplasmic dynein 1 generate a single motor assembly that can move processively for many micrometers along the microtubule before falling off.