Organelle cargo distribution is similar in wild-type cells (left) and cells expressing nonmicrotubule-binding dynactin (right), indicating that transport remains intact.
Dynactin retrieves microtubule motors such as dynein from the cytoplasm and docks them onto their cargo. Dynactin also anchors the minus ends of microtubules on the centrosome.
One dynactin isoform that is found in human neurons lacks its microtubule-binding domain (MBD). Kim and colleagues thus supposed that dynactin might be functional even without locking onto microtubules. They found that indeed cargo transport does not rely on the MBD.
With or without a functional MBD, dynactin helped move four different physiological cargos, including vesicles and proteins, just as far along microtubules and at the same velocity and frequency.
Dynactin's MBD...
