The BTB (Broad-Complex, Tramtrack and Bric a brac) domain, also known as the POZ (Poxvirus and Zinc finger) domain, is an N-terminal homodimerization domain that contains multiple copies of kelch repeats and/or C2H2-type zinc fingers. Proteins that contain BTB domains are thought to be involved in transcriptional regulation via control of chromatin structure and function. KLHL9 (kelch-like 9) is a 617 amino acid protein containing one BACK (BTB/kelch associated) domain, six kelch repeats and a BTB/POZ domain. KLHL9 is believed to play a role in protein ubiquitination and may function as a substrate-specific adapters of an E3 ubiquitin-protein ligase complex with CUL-3.