Figure 2.

Two distinct components are found in Xenopus extracts that are both required for Cdc42-induced actin polymerization. (a) Actin polymerization induced by Cdc42 in reactions containing MCAP1 or MCAP2 or both. (b) The time course of actin polymerization induced by Cdc42 or buffer by using combined MCAP1 and MCAP2 fractions (20 μl each). (c and d) Depletion of MCAP2 but not MCAP1 by Cdc42. Actin polymerization was assayed in fractions depleted by beads coated with GST-Cdc42 charged with different nucleotides (shown in parentheses). In each experiment, the depleted fraction (fraction names followed by nucleotides in parentheses) was tested in the presence of its untreated complementing fraction (fraction names only). GST-Cdc42-GTPγS beads were used in the visual assay (a and c), and Cdc42-GTPγS (25 nM) was used in the pyrene actin assay (b and d).