second type I K homology (KH) RNA-binding domain found in the family of NEDD4-binding protein 1 (N4BP1)
The N4BP1 family includes N4BP1, NYN domain and retroviral integrase catalytic domain-containing protein (NYNRIN) and KH and NYN domain-containing protein (KHNYN). These proteins are probably of retroviral origin. N4BP1 interacts with and is a substrate of NEDD4 ubiquitin ligase (neural precursor cell expressed, developmentally downregulated 4, E3 ubiquitin protein ligase). It is also an inhibitor of the E3 ubiquitin-protein ligase ITCH, a NEDD4 structurally related E3. N4BP1 acts by interacting with the second WW domain of ITCH, leading to compete with ITCH's substrates and impairing ubiquitination of substrates. NYNRIN, also known as CGIN1/Cousin of GIN1, may contribute to retroviral resistance in mammals by regulating the ubiquitination of viral proteins. KHNYN acts as a novel cofactor for zinc finger antiviral protein (ZAP) to target CpG-containing retroviral RNA for degradation. Members of this family contains two type I K homology (KH) RNA-binding domain. The model corresponds to the second one.