Dynactin-membrane interaction is regulated by the C-terminal domains of p150(Glued)

Dynactin has been proposed to link the microtubule-associated motor cytopla smic dynein with membranous cargo; however, the mechanism by which dynactin -membrane interaction is regulated is unknown. Here we show that dynein and dynactin exist in discrete cytosolic and membrane-bound states in the fila mentous fungus Neurospora crassa. Results from in vitro membrane-binding st udies show that dynein and dynactin-membrane interaction is co-dependent. p 150(Glued) of dynactin has been shown to interact with dynein intermediate chain and dynactin Arp1 filament; however, it is not known to play a direct role in membrane binding. In this report we describe our analysis of 43 p1 50(Glued) mutants, and we show that C-terminal deletions which remove the t erminal coiled-coil (CC2) and basic domain (BID) result in constitutive dyn actin-membrane binding. In vitro addition of recombinant p150(Glued) CC2+BD protein blocks dynactin-membrane binding. We propose that the C-terminal d omains of p150(Glued) regulate dynactin-membrane binding through a steric. mechanism that controls accessibility of the Arp1 filament of dynactin to m embranous cargo.