Intrinsic tethering activity of endosomal Rab proteins

Rab small G proteins regulate membrane trafficking events by recruiting effectors that mediate vesicle tethering. In vitro studies now suggest that Vps21 and other endosomal Rabs in budding yeast can undergo GTP-regulated Rab-Rab interactions that drive tethering in the absence of effectors, implying that they have an intrinsic tethering activity that may function in concert with conventional effectors.