Plays a key role in dynein-mediated retrograde transport of vesicles and organelles along microtubules by recruiting and tethering dynein to microtubules. Binds to both dynein and microtubules providing a link between specific cargos, microtubules and dynein. Plays a role in metaphase spindle orientation. Binds to microtubules and to cytoplasmic dynein. Binds preferentially to tyrosinated microtubules than to detyrosinated microtubules. Localizes to microtubule plus ends. Localizes preferentially to tyrosinated microtubules than to detyrosinated microtubules. At least 3 isoforms are produced. Ubiquitously expressed. Belongs to the dynactin 150 kDa subunit family.