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Substoichiometric Amounts of Aip1p Accelerate the Disassembly of Cofilin-Decorated Actin Filaments

Shown below is an actin filament pelleting assay: actin purified from yeast was induced to polymerize with salt and magnesium in the presence of stoichiometric amounts of cofilin and varying amounys of Aip1p. The filaments are then pelleted and the supernatant versus the pellet is sampled in a coomassie stained gel to quantify the amount of actin present in the filamentous form. As can be seen in lane 1, actin efficiently forms filaments in the presence of cofilin and these filaments are fully bound by cofilin as evidenced by the presence of cofilin in the pellet phase. The addition of Aip1p at a 1:5 stoichiometry causes a large decrease in actin from the pellet phase. Even a 1:200 ratio of Aip1p to actin and cofilin leads to a measurable decrease in filaments (lane 6) This assay shows that Aip1p can act to destabilize cofilin-decorated actin filaments even when present at vastly substoichiometric levels.