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. Author manuscript; available in PMC: 2017 Jun 10.
Published in final edited form as: Annu Rev Biophys. 2016 Apr 29;45:85–116. doi: 10.1146/annurev-biophys-070915-094206

Figure 1.

Figure 1

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.