Simple model of assembly dynamics of cytoskeletal filaments. Microtubules and
actin filaments are polar polymers composed of individual monomers that can be
added to or removed from their ends. In actin filaments, monomers can be added
to and subtracted from both the barbed (i.e., plus) ends and pointed (i.e.,
minus) ends. However, in vivo there is rapid addition of monomers at the barbed
end and net dissociation of monomers at the pointed end. In contrast, the
addition and removal of monomers happen primarily at the plus end of
microtubules. We abstract these two classes of cytoskeleton polymers into a
simplified model by considering idealized filaments for which monomer subunits
(orange) are added with rate r and
subtracted with rate γ. This results in the length
(l) of the filament evolving stochastically in time.
Reprinted with permission from Reference 43.