KLHL13 (kelch like 13), also known as BKLHD2 (BTB and kelch domain containing protein 2), is a 604 amino acid protein that contains six Kelch repeats and one BTB/POZ domain. Expressed predominantly in brain, KLHL13 is believed to play a role in protein ubiquitination and may function as a substrate specific adapter of an E3 ubiquitin protein ligase complex. E3 ligases accept a ubiquitin residue from an E2 ubiquitin conjugating enzyme and immediately transfer that residue to a protein that is targeted for degradation. Specifically, KLHL13 interacts with KLHL9 and CUL3, a member of the cullin family of mediators that participate in the selective targeting of proteins for ubiquitin mediated proteolysis. Via its BTB and C terminal Kelch (BACK) motif, KLHL13 is thought to play a role in spatially orientating substrates in the CUL3 ligase.