FIGURE 9.
Tmod3 preferentially sequesters cytoplasmic β- and γcyto-actin monomers in the presence of physiological salt, but Tmod1 does not. A and B, effects of Tmod1 (A) and Tmod3 (B) on F-actin sequestration in a sedimentation assay. 4 μm αsk-actin, β-actin, or γcyto-actin was polymerized in the presence of increasing amounts of Tmod1 and Tmod3 and ultracentrifuged to sediment F-actin. Because the recombinant cytoplasmic actins were produced using a baculovirus-driven expression system and contained 20–25% contaminating insect actin (41), we also tested pure insect actin as a control. Supernatants (s) and pellets (p) were analyzed by SDS-PAGE and Coomassie Blue staining. C and D, densitometric quantification of the percentage of actin in the supernatant of mixtures of Tmod1 and actin isoforms (C) or mixtures of Tmod3 and actin isoforms (D). Data shown are mean ± S.D. (error bars) of three experiments.