The structurally disordered KRAB repression domain is incorporated into a protease resistant core upon binding to KAP-1-RBCC domain.

The KRAB domain is a 75 amino acid transcriptional repression module that is encoded by more than 400 zinc finger protein genes, making it the most abundant repression domain in the human proteome. KRAB-mediated gene silencing requires a direct high affinity interaction with the RBCC domain of KAP-1 co-repressor. The structures of the free KRAB domain or the KRAB-RBCC complex are unknown.