The sites of positive selection lying within the BRC repeats of BRCA2 are located adjacent to the Rad51 binding region. A. The 8 BRC repeats of the human BRCA2 protein were aligned using ClustalX. The red and peach colored boxes are the motifs within the BRC repeats thought to facilitate binding with Rad51 . Residues 1008, 1225, and 1426 are colored in green, orange, and yellow, respectively. All three sites lie just adjacent to the FxxA motif which interacts with two hydrophobic pockets in the Rad51 oligomer. B. The co-crystal structure of BRC4 (blue) in complex with Rad51 (grey) is shown (PDB ID 1N0W ). The FxxA motif is depicted in red. Residues 1008, 1225, and 1426 are shown in green, orange, and yellow, respectively.