Abstract
Progress has been made recently in understanding certain aspects of the structure of the ER. It is very likely that kinesin, dynein, and myosin are associated with the ER and are responsible for distributing the fluid membranes of the ER by interaction of these motors with microtubules and actin filaments. Other kinds of structural protein associations with the ER are also likely, for instance, binding of cortical ER to subplasmalemmal regions or microtubule binding and/or polymerization along ER tubules.