Dynactin, a conserved, ubiquitously expressed component of an activator of vesicle motility mediated by cytoplasmic dynein

Steven R. Gill, Trina A. Schroer, Illya Szilak, Eric R. Steuer, Michael Sheetz, Don W. Cleveland

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Although cytoplasmic dynein is known to attach to microtubules and translocate toward their minus ends, dynein's ability to serve in vitro as a minus end-directed transporter of membranous organelles depends on additional soluble factors. We show here that a ∼20S polypeptide complex (referred to as Activator I; Schroer, T. A., and M. P. Sheetz. 1991a. J. Cell Biol. 115:1309-1318.) stimulates dynein-mediated vesicle transport. A major component of the activator complex is a doublet of 150-kD polypeptides for which we propose the name dynactin (for dynein acrivator). The 20S dynactin complex is required for in vitro vesicle motility since depletion of it with a mAb to dynactin eliminates vesicle movement. Cloning of a brain specific isoform of dynactin from chicken reveals a 1,053 amino acid polypeptide composed of two coiled-coil α-helical domains interrupted by a spacer. Both this structural motif and the underlying primary sequence are highly conserved in vertebrates with 85% sequence identity within a central 1,000-residue domain of the chicken and rat proteins. As abundant as dynein, dynactin is ubiquitously expressed and appears to be encoded by a single gene that yields at least three alternative isoforms. The probable homologue in Drosophila is the gene Glued, whose protein product shares 50% sequence identity with vertebrate dynactin and whose function is essential for viability of most (and perhaps all) cells in the organism.

Original languageEnglish (US)
Pages (from-to)1639-1650
Number of pages12
JournalJournal of Cell Biology
Issue number6
StatePublished - Jan 1 1991
Externally publishedYes


ASJC Scopus subject areas

  • Cell Biology

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