As described in lecture, cells form actin filaments in particular regions of the cell in part because they nucleate filament for
mation at particular times and places within cells and in part because they inhibit the formation of filaments that are "randomly" nucleated. What protein(s) is/are responsible for inhibiting the elongation of filaments that are randomly nucleated?a. Profilin b. Thymosin B4
c. Tropomodulin
d. Formin
e. CapZ
Cap Z is a capping protein which controls the access to the free barbed ends of actin filaments and is therefore a major factor affecting actin filament elongation
Capping proteins have a high affinity for barbed ends and their micromolar concentration in the cytoplasm ensures that most barbed ends are capped
Depletion of capping protein promotes increased filament assembly away from the leading edge in migrating cells
Cap Z helps favor actin assembly by preventing the loss of actin subunits to the barbed end and also prevent annealing of severed or de-branched filaments and they block both the association and dissociation of subunits at the barbed end
