Substrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3 ubiquitin-protein ligase complex required for mitotic progression and cytokinesis. The BCR(KLHL9-KLHL13) E3 ubiquitin ligase complex mediates the ubiquitination of AURKB and controls the dynamic behavior of AURKB on mitotic chromosomes and thereby coordinates faithful mitotic progression and completion of cytokinesis. {ECO:0000269|PubMed:14528312, ECO:0000269|PubMed:17543862, ECO:0000269|PubMed:19995937}. This is the function of KLHL9 (kelch like family member 9, Ensembl gene identifier ENSG00000198642).