Substrate-recognition component of a cullin-5-RING E3 ubiquitin-protein ligase complex (ECS complex, also named CRL5 complex), which mediates the ubiquitination and subsequent proteasomal degradation of target proteins (PubMed:25654263, PubMed:33268465). The ECS(ASB9) complex catalyzes ubiquitination of creatine kinases CKB and CKMT1A (PubMed:20302626, PubMed:22418839, PubMed:25654263, PubMed:33268465). {ECO:0000269|PubMed:20302626, ECO:0000269|PubMed:22418839, ECO:0000269|PubMed:25654263, ECO:0000269|PubMed:33268465}. [Isoform 2]: Does not interact with the Elongin BC complex, likely to be a negative regulator of isoform 1. . This is the function of Ensembl gene identifier ENSG00000102048 (ASB9, ankyrin repeat and SOCS box containing 9).