APC/C-Cdc20 binding is impaired in bub3Δ and bub3^R127A/R239A cells but not in bub1Δ, sgo1Δ, or bub1-ΔK cells. (A) Co-IP and input Western blot showing APC/C component Cdc23-3HA and Cdc20 in cells at the metaphase to anaphase transition. Cdc28 serves as a loading control. (B and C) Plots of the mean percentage of Cdc20 bound to Cdc23 (B) and levels of Cdc23 pulled down in the IP (C) from three independent experiments. Values were normalized to wild type. Error bars are the SD. Asterisks indicate a statistically significant difference compared with wild type (*, P < 0.001, unpaired t test with Welch’s correction).