Dynactin 5 (or subunit p25); Dynactin is a major component of the activator complex that stimulates dynein-mediated vesicle transport. Dynactin is a heterocomplex of at least eight subunits, including a 150,000-MW protein called Glued, the actin-capping protein Arp1, and dynamatin. In vitro binding experiments show that dynactin enhances dynein-dependent motility, possibly through interaction with microtubules and vesicles. Subunit p25 is part of the pointed-end subcomplex in dynactin that also includes p26, p27, and Arp11. This subcomplex interacts with membranous cargoes. p25 and p27 contain imperfect tandem repeats of a hexapeptide repeat motif (X-[STAV]-X-[LIV]-[GAED]-X), indicating a left-handed parallel beta helix (LbH) structural domain. Proteins containing hexapeptide repeats are often enzymes showing acyltransferase activity.