Figure 1.

BubR1 ABBA Motifs Bind Cdc20

(A) Alignment of the central region of the MAD3/BUBR1-like proteins showing an ABBA-KEN-ABBA cassette conserved across the majority of eukaryotic kingdoms. The inter-motif spacing d1 (ABBA²⁷²-KEN) and d2 (KEN-ABBA³⁴⁰) are also shown.

(B) Relative binomial logos created from the experimentally characterized ABBA motif instances and their flanking residues. Logos show the log⁻¹⁰ of the binomial probability (see Supplemental Experimental Procedures for details). Asterisks signify positions that show strong preferences for a particular amino acid or chemically similar grouping of amino acids (e.g., hydrophobic, aromatic, or acidic positions). Logos are split to emphasize the divergence of the specificity of the fungal Cdc20 from the metazoan Cdc20 and fungal Cdh1. See Supplemental Experimental Procedures for details.

(C) Biotin-labeled peptides encompassing the BubR1 ABBA motifs were incubated with extract from HeLa cells synchronized in metaphase. Peptides in which positions 3, 4, and 6 of the consensus ABBA motif were mutated to alanine (AAA) were included as controls.

(D) Cdc20 binding shown in (C) was quantified and the mean and SEM from three independent experiments are shown. See also Figure S1.